- Published in Features.
When CANbus was introduced in 1991 on the Mercedes-Benz S-Class, it linked five ECUs. The data that it was required to handle was minuscule, reflected in the CANbus’s transfer rate of just 500Kbit/s. Since then the number of ECUs in even a small car has grown exponentially and the data being collected and transferred around the vehicle is now enormous. The software capacity needed to run a human-machine interface can be as large as 1GB.
CANbus has improved. High-speed CAN systems can now transfer data at up to 1Mbit/s, and the introduction of Flexray has seen data transfer rates increase to 10Mbit/s. But carmakers are installing more data-hungry devices for entertainment and safety systems. High bandwidths are required when numerous cameras are placed around the vehicle to produce high-definition images for safety systems, for instance.
The MOST network, used primarily for infotainment systems, can run at rates of up to 150Mbit/s, but the technology is expensive as its sole market is the automotive industry.
Adapting technology from the consumer electronics sector would give OEMs and Tier One suppliers greater financial control over the systems and the ability to increase bandwidth to beyond 1Gbit/s. Rick Kreifeldt, vice-president of research at Harman, says: “The issue that’s coming into play in a big way is the amount of inter-device communications – it’s exploding. Before there were very separate domains – infotainment, driver systems and engine control for example – but now a lot more cross-domain communication is required, causing a real bottleneck.”
Using the higher bandwidths of Ethernet connection could help to address that challenge, and introducing it to the automotive sector should be relatively straightforward as it’s a well-established technology in other industries. When you switch on your computer and start checking your emails, the information is more than likely to have travelled through a high-speed Ethernet connection.
Kreifeldt says: “You’ve got the entire IEEE research behind Ethernet, and data centres really pushing the speed boundaries. If you wanted a 100Gbit/s link in a car, everything to do that exists today. There’s no invention needed.”
That lessens the investment risk for carmakers, while also making Ethernet highly scaleable, as Kreifeldt explains: “You have an easy migration path from lower speed to higher speed, so you can have cost-optimised nodes that use really low speed or you can have high-speed components that are all baked into normal Ethernet. That’s a massive advantage compared to moving from something like MOST25 to MOST50 to MOST150, where you’re redoing every node on the network.”
Cabling for an Ethernet-based system could also help to reduce costs and weight – 100Mbit/s networks can use inexpensive cable. Higher-speed systems where only one or two links at 1Gbit/s are needed can be easily accomplished with co-axial or fibre-optic cables, according to Kreifeldt.
What is uncertain is whether the technology will meet strict EMC requirements. Lars Reger, vice-president of automotive strategy at NXP, says: “The challenge is how do you make the transceivers robust, not only in temperature ranges of -40°C up to 200°C, but also how do you make them robust against cross-talk and radiation. Assume someone is entering the car with their mobile phone. You have a lot of radiation from the phone – how do you make sure that this does not kill your infotainment system or that your rear-view camera still works?”