10Base-T1S simplifies automotive zonal architectures

By Andreas Pellkofer and Madhura Deyanda Poonacha, Analog Devices

Automakers aim to provide vehicles with home-like comfort and entertainment, which raises demand for electronic control units (ECUs). Older bus technologies and electrical/electronic architectures struggle to keep up. 10Base-T1S Ethernet is transforming cars into fully connected experiences.

Automotive electronic control units (ECUs), which control each component of a vehicle’s operation, have grown rapidly since their first installation by Volkswagen in 1968. Automakers constantly add features that offer drivers and passengers a similar level of comfort and entertainment as at home or work. Thus, most bus technologies and electrical/electronic (E/E) architectures — some established decades ago — cannot keep up with the growing demand for ECUs to interact with each other and process large amounts of data.

Current vehicle ECUs are divided into almost isolated functional domains such as powertrain, chassis, infotainment, and comfort. Sensors and actuators are dispersed throughout the vehicle, and wires link to functional domain ECUs, as illustrated in Figure 1. Those wires increase the vehicle’s complexity, cost, and weight. Bundled into cables, these wires significantly impact the vehicle’s range.

Now decades old, technologies such as controller area network (CAN), FlexRay, and local interconnect network (LIN) facilitate communication between various ECUs and simple sensors or actuators. High-speed Ethernet provides communication between different domains. To facilitate data transfer between different bus technologies, vehicles use expensive dedicated gateways within the ECUs.

The architecture’s complexity expands as the number of features increases. Extending existing features or introducing new ones necessitates significant development, implementation, and testing. Original equipment manufacturers (OEMs) aim to accelerate innovation while reducing costs and generating post-revenue sales. A vehicle has significantly longer development cycles than other consumer products, such as mobile communication devices. Breaking the link between hardware and software toward a software-defined car is a target of many OEMs. Two significant challenges – static functional domain architecture and wiring complexity – prevent realizing this vision.

Going zonal

A zonal-based architecture divides the vehicle into zones (Figure 2). Local ECUs serve all functions regardless of the domain. These ECUs connect to zonal controller devices, which concentrate processing power in several units across the vehicle. Communication between zonal ECUs and the high-performance computing units occurs through high-speed point-to-point links. According to CARIAD (a subsidiary of Volkswagen Group), this will replace over two dozen ECUs and wiring harnesses that are longer than a kilometer.

With cutting-edge technology transforming vehicle design and performance, the automotive industry is experiencing a significant vehicle network architectural transition. Implementing technologies such as vehicle-to-vehicle communications, augmented reality dashboards, and self-driving adds complexity, cost, and the need for more electronics. By 2030, it is estimated that these technologies will increase automotive electronics by up to 45%.

With the introduction of zonal architecture, numerous electrical components and control systems are consolidated and centralized into predetermined zones within the vehicle. Nodes become dependent on their location and not on their functional ECUs. This simplifies the network, resulting in less weight and increased fuel efficiency. This architecture simplifies scaling because new features and systems may be added without requiring extensive modifications. Over-the-air software upgrades may be made more efficient by delivering through the vehicle’s central computer unit. OEMs may now remotely enhance features by offering customization to the customer and adopting post-sales strategies such as advanced driver-assistance systems (ADAS), autonomous driving, comfort, and infotainment features.

Bridging the challenges

Legacy bus technologies lack the performance capabilities, such as throughput and quality of service, required in this new architecture. Now, another well-established technology has entered the automotive industry: Ethernet.

Ethernet has evolved with the demand for higher data rates for decades by developing new physical layers (PHYs), thereby keeping the higher (protocol) layers compatible. Some speed grades even work on identical harnesses. Network features are serviced by higher protocol layers, mainly in software.

Initially, Ethernet was not specifically tailored for automotive environments, for it lacked features that included electromagnetic compatibility (EMC) and power efficiency. Also, using shielded cables with two or four pairs of wires contradicts the goal of saving weight. The automotive industry standardized a single twisted-pair cable solution, prompting the need to develop new PHY technologies that meet all the demands of an automotive communication link.

This led to the development of the xBASE-T1 automotive Ethernet standards (T1 stands for a single twisted pair cable). Different data rates are supported for ECU interconnects. In addition, the crossing between different speed grades is handled by simpler devices: switches. This promotes a reduction in the number of expensive gateways.

Although zonal architecture provides a comprehensive platform for all network technologies, issues remain with adaptation to homogenous network architecture, boot time, achieving latency, and throughput. With about 90% of network nodes running at rates of up to 10 Mb/sec, legacy automotive network technologies that were once sufficient are now incapable of achieving the required throughput. These constraints impede the smooth integration of advanced in-vehicle systems. As a result, there is an increasing demand for creative solutions to ensure quick response times and improve overall performance.

Effective implementation of 10Base-T1S

Extending Ethernet to the edge node gives the system a robust network and simplifies packet movement. 10Base-T1S is defined in IEEE 802.3cg, and OEMs have begun to implement this Ethernet PHY technology, with plans to have it on the road by 2025. The OPEN Alliance, a working group, built its specifications to augment the IEEE standard, aiming to encourage the widespread adoption of Ethernet in automotive industries. Like other automotive communication technologies, 10Base-T1S can operate in multidrop mode configurations. The bus employs a new access technique called physical layer collision avoidance (PLCA) on top of carrier-sense multiple access with collision detection (CSMA/CD) to avoid bus collisions. PLCA ensures that latency remains within predictable bounds while maximizing throughput and network efficiency.

Using 10Base-T1S in some standard, system-critical applications reduces system complexity, allowing faster and more efficient data transfer within vehicles. These extended system benefits include cost reduction, enhanced security, a unified communication mechanism without the need for complex gateways, and the option of power over data lines, ensuring a smooth integration into the forthcoming generation of software-defined vehicles.

Conclusion

The transition from existing automotive domain-based design to zonal architecture marks a significant advancement in the automobile industry. Zonal architecture offers greater flexibility and scalability. It enables the centralization of software, minimizes wiring, enhances fuel efficiency by decreasing weight, and maintains cost-effectiveness. Implementing Ethernet consistently throughout the vehicle simplifies network complexity compared to using a combination of technologies. Including 10Base-T1S, automotive Ethernet extends automotive Ethernet to the vehicle’s edge, reducing the need for expensive gateways.