Ethernet In Cars

Why just adding more bandwidth isn’t enough to deal with the growing volume of data.


The automobile is encountering possibly the biggest changes in its technological progression since the invention of the internal combustion engine nearly 150 years ago. Increasing levels of autonomy will reshape how we think about cars and car travel. It won’t be just a matter of getting from point A to point B while doing very little else — we will be able to keep on doing what we want while in the process of getting there.

As it is, the modern car already incorporates large quantities of complex electronics – making sure the ride is comfortable, the engine runs smoothly and efficiently, and providing infotainment for the driver and passengers. In addition, the features and functionality being incorporated into vehicles we are now starting to buy are no longer of a fixed nature. It is increasingly common for engine control and infotainment systems to require updates over the course of the vehicle’s operational lifespan.

Such an update is the one issue that proved instrumental in first bringing Ethernet connectivity into the vehicle domain. Leading automotive brands, such as BMW and VW, found they could dramatically increase the speed of uploads performed by mechanics at service centers by installing small Ethernet networks into the chassis of their vehicle models instead of trying to use the established, but much slower, Controller Area Network (CAN) bus. As a result, transfer times were cut from hours to minutes.

As an increasing number of upgradeable Electronic Control Units (ECUs) have appeared (thereby putting greater strain on existing in-vehicle networking technology), the Ethernet network has itself expanded. In response, the semiconductor industry has developed solutions that have made the networking standard, which was initially developed for the relatively electrically clean environment of the office, much more robust and suitable for the stringent requirements of automobile manufacturers. The CAN and Media Oriented Systems Transport (MOST) buses have persisted as the main carriers of real-time information for in-vehicle electronics – although, now, they are beginning to fade as Ethernet evolves into a role as the primary network inside the car, being used for both real-time communications and updating tasks.

In an environment where implementation of weight savings are crucial to improving fuel economy, the ability to have communications run over a single network (especially one that needs just a pair of relatively light copper cables) is a huge operational advantage. In addition, a small connector footprint is vital in the context of increasing deployment of sensors (such as cameras, radar and LiDAR transceivers), which are now being mounted all around the car for driver assistance/semi-autonomous driving purposes. This is supported by the adoption of unshielded, twisted-pair cabling.

Image sensing, radar and LiDAR functions will all produce copious amounts of data. So data-transfer capacity is going to be a critical element of in-vehicle Ethernet networks, now and into the future. The industry has responded quickly by first delivering 100 Mbit/s transceivers and following up with more capacious standards-compliant 1000 Mbit/s offerings.

But providing more bandwidth is simply not enough on its own. So that car manufacturers do not need to sacrifice the real-time behavior necessary for reliable control, the relevant international standards committees have developed protocols to guarantee the timely delivery of data. Time Sensitive Networking (TNS) provides applications with the ability to use reserved bandwidth on virtual channels in order to ensure delivery within a predictable timeframe. Less important traffic can make use of the best-effort service of conventional Ethernet with the remaining unreserved bandwidth.

The industry’s more forward-thinking semiconductor vendors, Marvell among them, have further enhanced real-time performance with features such as Deep Packet Inspection (DPI), employing Ternary Content-Addressable Memory (TCAM), in their automotive-optimized Ethernet switches. The DPI mechanism makes it possible for hardware to look deep into each packet as it arrives at a switch input and instantly decide exactly how the message should be handled. The packet inspection supports real-time debugging processes by trapping messages of a certain type, and markedly reduces application latency experienced within the deployment by avoiding processor intervention.

Support from remote management frames is another significant protocol innovation in automotive Ethernet. These frames make it possible for a system controller to control the switch state directly. For example, a system controller can automatically power down I/O ports when they are not needed – a feature that preserves precious battery life.

The result of these adaptations to the core Ethernet standard, as well as the increased resilience it now delivers, is the emergence of an expansive feature set that is well positioned for the ongoing transformation of the car, taking it from just being a mode of transportation into the data-rich, autonomous mobile platform it is envisaged to become in the future.

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