The increasing complexity of automotive systems, from diagnostic sensors to infotainment components, creates a need for more robust data networking. Two companies, Micrel and Marvell, recently announced a means of using Ethernet to address at least part of this issue.
Since the 1990s, cars have employed the CAN bus standard to send data between sensors and engine controllers. However, more airbags and the addition of safety technologies such as vehicle stability control tax the capabilities of the CAN bus standard's 1 megabit per second data rate.
To move forward, companies are looking at developing more robust networking capability in the car. The FlexRay consortium, now defunct, produced a specification that allows 10 megabits per second data to flow around the car. The FlexRay spec was designed for mission-critical applications with minimal data lag, but its adoption has been slow. BMW currently uses it for the and performance vehicles.
Ethernet has the potential to move data at much higher rates, 1 gigabit per second, similar to current home and office networks. In a conversation with CNET, Michael Jones, senior product manager for Micrel, pointed out that economies of scale make Ethernet hardware less expensive than other solutions, an attractive feature for automakers and consumers alike.
Currently, only BMW has implemented Ethernet in a production vehicle, using it as the data network for diagnostic systems. Ethernet has been difficult to deploy due to its electromagnetic emissions, which do not comply with automotive standards. Shielded cables work, but are expensive.
Micrel and Marvell have both come up with compliant solutions using simple twisted-pair cables, like the CAT-5 cabling used in most Ethernet networks. The Ethernet standard was designed to transmit over 100 meters of cabling. As cable distances in cars are much shorter, the companies each developed filters to reduce the strength of the signal through the wires, limiting emission without losing integrity over shorter distances.
Jones suggests that the initial deployment of this type of Ethernet in the car would be for something like a surround-view camera system. For example, a car could have cameras on the rear, front, sides, and in place of side mirrors, each sending their signals to displays in the cabin using the Audio Video Bridging standard (AVB) over Ethernet.
Beyond that, Ethernet would work well with infotainment systems in cars, systems which mirror work that has already been done in developing AVB for homes. Jones says that Micrel's Ethernet switches and transceivers are already being developed to automotive standards, which require being able to withstand temperatures from minus 40 degrees 125 degrees Celsius, and harsh shocks.
However, Jones says that AVB has too much lag to work in the kind of mission critical systems for which FlexRay was designed. There is work being done on a next generation AVB standard that would more tightly control signal transmit times, making it suitable for not only antilock braking and vehicle stability, but complete drive-by-wire systems.
That a future car might have an Ethernet backbone made up of 10 Ethernet switches transmitting data for everything from a backup camera to power steering calibration will raise security concerns. Jones says that virtual, separate networks can be run securely on Ethernet switches, pointing out current examples from the military and banking.
While the announcements by Micrel and Marvell look promising, the future of networking vehicle components has not yet been determined. The 1394 Trade Association (think Apple FireWire) is promoting its standard for use in automotive applications.