Signals such as video, radar, etc. are also transmitted via Ethernet. The trend is to replace the CAN bus as the automotive bus, but is this really the case?

At the moment, the Internet is full of articles saying that "Ethernet will replace the CAN bus as the only bus in the car". Is this true?

Let's start with the answer at the beginning of the article:

As far as current human technology is concerned, Ethernet can only be used in vehicles as a complement to the CAN bus, and there is no possibility of replacing the CAN bus for the time being.

If you are not satisfied with just knowing the conclusion, what you know and why you know it, then read the next article. It may take 3 minutes of your time, but it will show you the reasons for coming to that answer.

As you know, as a standard open network Ethernet transmission signal compared to CAN bus has a high transmission rate, long transmission distance and other advantages in. And the technology has been quite mature, mastered by more people. But at present, even if it has been used in the car but only for the transmission of radar, video and other high-speed signals. Why can't we make a car that uses Ethernet bus communication? The main reasons are as follows:

1、Security of CAN Network

In terms of network connectivity, the CAN bus is connected via physical signals, whereas Ethernet is a switch connection. The switch is necessary for the Ethernet connection, and if the switch fails, the whole network collapses. It would be easy to leave the security of the entire network in the hands of a switch that is too fragile, and it would be costly to set up redundant backups. The CAN bus, on the other hand, is a very simple structure, just two wires to pull, simple and robust. For safety-first cars, the CAN bus is undoubtedly more suitable. In addition, Ethernet adopts a timeout retransmission mechanism, the failure of a single node can easily spread to the whole network, compared with the hierarchical arbitration system of CAN bus is also much inferior.

2. Cost Decision for CAN

We mentioned switches in the context of security. Yes, the presence of an Ethernet network switch is essential, and the number of nodes in a modern automotive network is so large that one or more switches with multiple interfaces would be required if Ethernet were used for all communication. In addition, because a car is a safety-critical product, the stability and quality of the switch must be extremely high, adding more than a fraction of a cent to the cost. Increasing costs is not something that car manufacturers want to see.

3、Software Stability

If you've seen the film 'Fast and Furious 8', you'll remember the 'zombie car' episode. The villain takes control of a large number of cars in New York City with 'self-driving' capabilities through hacking technology and rushes into the streets to attack the Russian ambassador, who is in possession of important documents. While the plot of the entertaining film does not stand up to scrutiny, the fact remains that networked cars can be exploited by hackers. Ethernet as a standard open network system compatibility and interoperability is good, the ability to share resources is strong, can easily complete the information and resource sharing operations. Undoubtedly, it reduces the cost of the malefactor's operation and improves the operability. Comparatively, CAN bus is a dedicated field bus, which is difficult for hackers to penetrate.