Ethernet: a critical enabler
Vehicle manufacturers are increasingly using sophisticated electronic systems to deliver enhanced driver safety and convenience. As a result, the modern car can contain anywhere between 30 and 100 electronic control units (ECUs), supporting functions such as safety, engine management, navigation and infotainment. Advanced driver-assistance systems (ADAS) are one of the fastest-growing segments in automotive electronics and, as their use grows, the large amount of data generated and shared by them is putting pressure on in-car connectivity systems. Existing automotive serial bus technologies are unable to support ADAS data rates and bandwidth requirements and are unable to scale to provide the future proof platform required by car manufacturers.
As with the office and, more recently the factory, the ubiquitous Ethernet protocol offers a potential solution, but has drawbacks in terms of real-time capability and its ability to handle automotive EMI and environmental conditions.
In addition to supporting the higher data volumes and rates generated by ADAS, replacement of traditional wiring harnesses with automotive Ethernet offers several benefits, including up to an 80% reduction in connectivity costs and up to 30% in cable-weight saving.
This new Ethernet standard changes established testing procedures and suppliers, system developers and manufacturers in the automotive eco-system must ensure that comprehensive physical layer, protocol, conformance testing, security, and harness testing are in place. A range of modern testing solutions are available to systems developers to simplify and speed testing and reduce time to market.
Evolution of in-car technology
Adoption of in-car technology continues apace with automotive electrical systems becoming more complex, enabling applications such as infotainment, ADAS, power trains and body electronics. In the last decade, the amount of ECUs, contained in the average new car has more than doubled, in complexity and volume.
Safety is a key driver of this technology with a range of applications emerging, including adaptive cruise control (ACC), followed by automatic emergency braking (AEB), blind-spot detection (BSD) and lane-change assist (LCA), vehicle-exit assist (VEA), and pre-crash warning (PCW).
These applications rely on advanced sensing technology, including radar, cameras, LiDAR and ultrasonics, Figure 1, which provide the respective ECU with accurate and timely information on the car’s environment and surroundings, enabling preventative or corrective actions to be taken.
These systems collect, process, generate and share vast amounts of data—as much as 4 TB per day according to some analysts—putting pressure on existing on-board wiring systems and communication protocols.
Emergence of the automotive Ethernet
This evolution in automotive technology has driven the development of a number of serial bus systems, (Table 1), each with their own characteristics and aimed at supporting different applications. The growth in new applications, each with specific communications requirements, quickly led to a situation where the car wiring harness had become the third heaviest and third most costly component of the average car, accounting for as much as 50% of assembly costs.
> Table 1. Common Automotive Serial Bus Technologies
|CAN (Controller Area Network)||1983||Shared serial bus supporting up to 1-Mbps data rates. Cost effective & reliable but is based on shared access and suitable only for low bandwidth applications. Typically used in powertrain, chassis and body electronics.|
|LVDS (Low Voltage Differential Signaling)||1994||Point-to-point link used mainly for camera and video data. Can only interface with on device at a time.|
|LIN (Local Interconnect Network)||1998||Low data-rate, 19,200 bps, based on master-slave architecture. Used mainly in body electronics, e.g. mirrors, power seats and accessories.|
|MOST (Media Oriented Systems Transport)||1998||
Ring architecture supporting up to 150 Mbps on fiber or copper
Each ring can host up to 64 devicesHigh bandwidth but also high cost
Shared serial bus running up to 10 MbpsTypically used in high-performance powertrain and safety systems, e.g. drive-by-wire, active suspension and adaptive cruise control
|CAN FD (Flexible Data-Rate)||2012||
Extension to CAN, to support higher bandwidthEnables more accurate and near-real-time data
This cost and complexity of the in-vehicle network was beginning to impact the time needed to get new cars to market. Additionally, the legacy serial bus systems were struggling to support the rapidly growing data throughput and capacity needs of the emerging applications.
Having identified the requirement for a high-bandwidth, scalable network, based on a future-proof open architecture, the industry developed a customized variant of Ethernet technology that met automotive EMC requirements while saving weight by using a single twisted pair.
Initially limited to diagnostic testing and firmware updates, the growing capabilities of automotive Ethernet have driven an expansion of its use within the modern vehicle, from peripheral functionality, such as diagnostics and firmware upgrades, to becoming the in-vehicle backbone network.
Testing of advanced automobile systems
Successful implementation of any system using automotive Ethernet requires a comprehensive test plan, supported by an appropriate testing solution. Figure 2 shows the complete automotive Ethernet stack.
At the physical layer, Figure 3, three points must be tested to validate compliance - the transmitter, the receiver, (integrated into the Ethernet PHY), and the link itself, which includes the wire harness and any connectors.
Test solutions are available for each point, which minimize test complexity and testing time. Transceiver testing solutions are available which enable automatic configuration and pre-packaged set-up of compliance tests. Modern test equipment also provides graphical output displays, showing connections to the device under test as well as printable pass/fail HTML reports.
Complete testing at the link level must cover cable continuity, connector integrity and must validate crosstalk levels across the entire communication channel.
At the higher levels of the stack, solution testing methodologies must validate the automotive TCP/IP stack as well as functionality such as time synchronization, (IEEE 802.1AS), audio video bridging transport, (802.1 Qav) and scheduled traffic transmission, (IEEE 802.1 Qbv)
The modern car is packed with electronics supporting driver safety and convenience and, as autonomous driving technology and connected car systems continue to evolve, the automotive Ethernet promises to hold the key to in-car networking challenges. While automotive Ethernet addresses the high data rates, bandwidth and EMI requirements of in-car electronic systems, it also brings new challenges for testing and implementation.
Effective testing at each layer of the automotive Ethernet stack is essential to support rapid diagnostics and establish confidence in the system or subsystem. Organizations such as Keysight Technologies provide a range of innovative test solutions and support to the system designer, developer, and integrator. Its software solutions provide a comprehensive set of Ethernet compliance software to test the four different automotive Ethernet standards; BroadR-Reach, IEEE 100BASE-T1, IEEE1000BASE-T1 and the One-pair-Ether-Net (OPEN) Alliance ECU.