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Industrial Ethernet Book Issue 101 / 8
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Automotive-grade Ethernet paves way for new era in cars

Ethernet has been slow to enter the automotive market but this is changing in areas such as vehicle diagnostics and flash downloads. A standards-based approach is one of the reasons why Ethernet is growing in automotive, making it easier for repair personnel to service cars from different manufacturers.

THE CONCEPT OF AUTONOMOUS DRIVING has never been more real as carmakers make use of the latest technologies for connectivity, multimedia, sensors and real-time processing. However, to create true autonomy, automakers need a better way to manage, control and distribute the massive amounts of data needed.

A distributed vehicle network provides a robust, flexible and cost-effective way to support the increasingly complex, high- bandwidth applications required to make self-driving cars a reality.

Networking technology for cars

Today′s cars are highly refined systems, equipped with dozens of electronic control units (ECUs), transmitters, receivers, actuators, sensors and other electronic components. They work in concert to improve the car - making it safer, more connected, more comfortable, more energy efficient and environmentally friendly and of course, easier to drive.

Using automotive Ethernet, data from cameras and sensors is sent to a central fusion box for synchronisation and further processing.

Many of these automotive components are used to provide some level of support to the driver through Advanced Driver Assistance Systems (ADAS). These various ADAS features give a glimpse of what autonomous driving will be like, as the car itself uses data collected from various sensors and electronic subsystems, to keep everyone safe.

With automatic cruise control, for example, the car automatically slows down or speeds up in response to other vehicles on the road. With adaptive light control, headlights can swivel and rotate on their own, to better illuminate the roadway as the car moves through corners and turns. There are cars that use cameras to show the driver what′s in a blind spot, cars that alert the driver if they drift into another lane and cars that can park themselves.

Managing and distributing the data required for autonomous driving in a cost-effective, efficient way will be a significant challenge and will add to what is already a complex task. ADAS functions, which make heavy use of cameras, radar and other sensors, can strain the data capacity of the in-vehicle network (IVN); while the onboard entertainment system adds its own requirements for bandwidth. As the evolution of ADAS and infotainment progresses, autonomous driving will require even more bandwidth.

Consider, for example, object detection. It makes it possible for the car to identify hazards and avoid collisions. Providing the car with the data needed to accurately monitor the external environment in real time requires the use of multiple high-resolution cameras, each sending large amounts of data for further processing. The car′s network must be both fast enough and powerful enough to keep up, or the feature won′t work properly.

Automotive Ethernet is becoming a recommended choice for high-bandwidth operations in the car.

Today′s IVN technologies

Today, cars use a mix of network protocols. This is because automotive-network technologies have evolved over time and because extra bandwidth usually has a higher price tag, so designers typically only install the bandwidth needed for a given task. Some of the network protocols currently used in vehicles were designed specifically for automotive use, while others were adopted from other areas, like computing and consumer electronics.

Using multiple network protocols in a single car can make the design harder to develop and maintain, but the trend is likely to continue as designers can save money and increase efficiency when they match the technology to the task.

Designers typically use relatively inexpensive, low-bandwidth protocols, such as LIN and CAN, for the straightforward tasks of body control and powertrain operations. The more expensive, higher-bandwidth protocols, such as FlexRay, MOST, LVDS, and Ethernet are reserved for more complex tasks that require higher data rates and more deterministic behaviour.

While LIN & CAN are complimentary to higher bandwidth technologies such as FlexRay or Ethernet, they can also work adversely to create bottlenecks in some situations, especially when working with larger ECUs. They remain the protocol of choice for many important, low-bandwidth control functions. At the other end of the spectrum, automotive Ethernet is a solution that combines the advantages of LVDS and MOST on a single Unshielded Twisted Pair (UTP) cable that is thinner, lighter and less expensive than either option. Automotive Ethernet is different from the standard Ethernet used in LANs. The next section describes these differences and explains why automotive Ethernet is our recommended choice for high-bandwidth operations in the car.

Today′s cars use a mix of network protocols. Automotive-network technologies have evolved, and designers typically only install the bandwidth needed for a given task.

The case for Automotive Ethernet

In the more than 40 years since it first came on the scene, Ethernet has been adopted by industries beyond computing and is doing a lot more than just connecting PCs and laptops together. Ethernet is used for Voice over Internet Protocol (VoIP) applications in telecom, for robotics and other automation applications in industrial and manufacturing as well as for safety-critical applications in avionics. But Ethernet has been relatively slow to enter the automotive market.

This is changing. For vehicle diagnostics and flash downloads, Ethernet is replacing CAN and even FlexRay in several situations. In fact, many cars today already have a Fast Ethernet port for flashing ECUs at the end of the assembly line, or for connecting the vehicle to diagnostic equipment at a garage.

These ports save time, since they transfer data at a faster rate, and that helps save costs in production and during service calls.

For diagnostics, Ethernet complies with ISO 134000. This defines a format based on Internet Protocol for vehicle diagnostics. It also complies with ISO 14229 which specifies a Unified Diagnostic Service (UDS) for control of the diagnostic functions used with vehicles. This standards-based approach is one of the reasons why Ethernet has grown in automotive, since standardised operation makes it easier for repair personnel to service cars from different manufacturers.

The standard version of Ethernet - meaning the version used with LANs, robots and other equipment - is not automotive friendly which limited its use as an IVN technology. Standard Ethernet uses CAT 5 cabling, which has four unshielded twisted pairs. It′s bulky, heavy and expensive. The electromagnetic emissions of standard Ethernet are high enough that it interferes with FM radio reception. Shielding the cable prevents this interference, but adds to the cost and weight. Standard Ethernet deals with the electronically noisy environment of a car with extra digital signal processing (DSP) operations.

Roadmap to 1 and multi Gbit/s

100 Mbits/s is only the beginning for automotive Ethernet. The IEEE is working on an automotive grade Ethernet PHY that can support data rates up to 1 Gbit/s. The aim is to accommodate increasingly sophisticated applications that require higher bandwidth, whilst eliminating potential interoperability issues between different bandwidth versions.

On the other hand, 10 Mbits/s Ethernet is expected to substitute FlexRay, simplify network protocols and reduce cabling cost. Object detection is one of the primary applications for Gigabit Ethernet since it supports uncompressed video. The layered structure of Ethernet will make it relatively straightforward to upgrade cars to the higher bandwidth once it becomes available.

Automotive Ethernet makes it possible for multiple systems to simultaneously access high bandwidth over a single UTP cable. Ethernet can become the backbone of the vehicle network, supporting higher levels of data processing and enabling more types of communication. The use of Traffic Engineering features like VLANs means each port receives dedicated bandwidth and the entire backbone is capable of IP connectivity. Body Domain, Infotainment and ADAS functions all could reside on the same physical network, but use logically separated virtual networks. This creates a more solid platform for development of the next-generation functions that will enable autonomous driving. Also, since advanced diagnostics are available for each link, the network is more robust and easier to manage.

ECUs are structured in a hierarchical architecture where application domains are connected through a data highway. Automotive Ethernet provides all the prerequisites of this holistic approach. It can connect the various application domains as well as the sub-networks that require higher bandwidth. A switched Ethernet network uses point-to-point communication to deliver bandwidth more efficiently than the broadcast communication used by protocols like CAN and FlexRay. The switching concept bridges domain boundaries without the kinds of time- consuming packing and re-sorting required by complex gateways.

A brief look at two applications, infotainment and 360-degree surround view, are good examples of how automotive Ethernet, can improve performance while making the vehicle design more efficient in a distributed network architecture.

Infotainment centers

Typically mounted somewhere in the dashboard, the head unit is a densely- integrated hardware interface that provides a single point of control for the vehicle′s entertainment media. The head unit supports all the infotainment features, ranging from AM/FM radio, digital terrestrial (e.g. HD-Radio, DAB, DRM), satellite radio (e.g. SXM), and MP3 playback; to GPS navigation, Bluetooth, rear-view display, odometer information, trouble warnings and more.

This type of centralised head unit tends to combine two things: a human-machine interface (HMI) and a vehicle-specific box. The HMI lets the driver or passenger make selections and revise settings and resembles recent consumer technologies such as smartphones. The vehicle-specific box contains broadcast reception and processing, connectivity functions for streaming music and the audio amplifier system. There are several drawbacks to the centralised approach. To begin with, the technologies housed in a head unit can have varying life spans.

Consumer technologies often have shorter life spans and need to be changed or upgraded more regularly than technologies for more vehicle-specific functions. Due to the dense integration of the box itself, upgrading or changing components can be difficult. Another significant challenge is that they need to be sized for the space available in the dashboard console and this often leads to a cramped design that needs to be protected from overheating. Adding functions makes it harder to eliminate heat from the box. Manual fans are typically used to remove the heat, but this adds cost and can introduce reliability issues.

By using automotive Ethernet in a distributed vehicle network, components can be moved out of the head unit and placed closer to where they′re needed. Smaller modules can be installed throughout the vehicle, opening up space in the head unit while also increasing operational efficiency and performance. For example, the tuner module can be placed closer to the antenna.

This not only reduces heat in the head unit/dashboard, but also reduces cabling costs significantly. Premium cars are another example, since they often require as many as four separate radio antennas and each antenna is connected to its own coax cable.

Running coax cable from the head unit to the antenna can be expensive and adds weight to the car. With Ethernet in a distributed network, the telematics unit can be integrated with the antenna module, for a less congested head unit and a design that uses less coax cable.

Over time, a V2X module, which manages communication with other vehicles and the infrastructure, can be added too. Another consideration is that moving the antenna module out of the head unit creates space to add embedded security to the design, to ensure that communication protocols take place in a secure, protected environment.

Cars now have many cameras to assist the driver for functions such as parking assistance and collision avoidance.

360-degree surround view

Cars now have as many as five video cameras to assist the driver. These cameras are currently used for things like parking assistance and collision avoidance and will be needed for object detection, to identify obstacles and other cars, as driving becomes more autonomous.

Using automotive Ethernet in a distributed vehicle network, data from the cameras and other sensors is sent to a central fusion box for synchronisation and further processing. An Ethernet switch enables deterministic (time-synchronous) routing of data packages through the network.

This is important because it supports the real-time processing required to have the car and driver see things as they happen. There are a number of other Ethernet features that help streamline the process. Low-power idle (LPI) and wake-up functionality save energy when the cameras aren′t in use, and Power over Data Line (PoDL) can make the wiring harness lighter by eliminating the extra lines for power. Quality of service, latency control, and bandwidth reservation for traffic flows also contribute to accuracy and performance.

The small footprint and flexible network characteristics of Automotive Ethernet mean that functions can be placed where they′re needed, anywhere in the car. This gives developers the freedom to create better designs while using fewer cables. Distributing functionality throughout the vehicle, yet keeping it connected to the backbone network, results in less weight, lower cost, and a higher degree of upgradability.

Distributed vehicle networks support increasingly complex, high-bandwidth applications such as vision systems, and infotainment that will become important components of increasingly connected cars. These networks will help make self-driving cars a reality and they will grow in importance over the next few years.

Günter Sporer, NXP Semiconductors.

Source: Industrial Ethernet Book Issue 101 / 8
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