Replacing CAN bus, will automotive Ethernet 10BASE-T1S become mainstream?

Under the trend of the new four trends of automobiles (electrification, networking, intelligence , and sharing) and software -defined automobiles, automobiles are undergoing a profound architectural change. The previous distributed architecture can no longer meet the increasingly complex functional requirements of automobiles. Automotive electronics and electrical systems are accelerating their evolution towards domain architecture, cross-domain architecture, and centralized architecture. Avnet pays close attention to the trend of automobile transformation and actively deploys automobile-related solutions with partners to help customers build the next generation of intelligent connected vehicles .

The driving force behind the evolution of automotive architecture is the exponential growth in the number of electronic control units ( ECUs ) in the car. From an average of 20-30, it has soared to more than 100, or even hundreds. The huge number of ECUs has brought severe challenges to the in-car network: slow data transmission , high latency, and poor reliability have seriously restricted the upgrade and development of automotive functions. A study by McKinsey shows that more than half of automotive customers (64%) are willing to change automakers to obtain better autonomous driving capabilities. It is expected that by 2030, 95% of new cars sold will be connected.

In order to meet these needs and challenges, the in-vehicle network must also be upgraded. According to the 2023 China Smart Electric Vehicle In-vehicle Communication Research Report by iResearch, the current in-vehicle bus communication is gradually changing from a distributed architecture of "CAN bus as the main and other buses as the auxiliary" to a domain-centralized architecture of " Ethernet as the main and CAN and other buses as the auxiliary".

Current in-vehicle network technology: CAN bus is the main

The in-vehicle network (IVN) is the lifeblood of modern cars and provides a key enabler for their versatility. It is responsible for transmitting various data streams, supporting advanced driver assistance systems ( ADAS ), infotainment systems, cameras , inter-vehicle communication systems , and remote sensing technologies such as radio waves, radars , and light detection, lidar , enabling cars to perceive the environment, assist driving, and provide rich entertainment functions.

At present, the in-vehicle network mainly adopts a variety of bus technologies such as CAN, LIN, FlexRay, MOST, LVDS and in-vehicle Ethernet . Among them, the CAN bus has become the most widely used standard protocol due to its low cost, reliability and easy implementation. It is widely used in the fields of body control, power system management, chassis control, etc. The LIN bus is a low-cost universal serial bus, which is often used in door, sunroof, seat control, etc., providing auxiliary functions for the CAN bus.

However, with the surge in the number of automotive electronic products and the continuous upgrading of their functions, CAN bus technology has been unable to meet the needs of modern automotive networks for high-speed, real-time, and bidirectional data transmission due to its half-duplex communication mode and limited transmission rate. In addition, the complex topology of traditional buses and redundant protocol layers have also made vehicle wiring harnesses increasingly large. Some vehicle wiring harnesses are up to 2.5 miles long, and the miles of copper wires in a typical car weigh up to 132 pounds (60 kilograms). For electric vehicles, the weight of the wiring harness directly affects their mileage, so reducing vehicle wiring is particularly important.

The automotive industry needs to replace the "aging" CAN protocol. As the fastest communication solution among all types of buses, automotive Ethernet may become an important communication technology for in-vehicle networks due to its high bandwidth, lightweight wiring harness and high cost-effectiveness.

Replacing CAN bus? 10BASE-T1S becomes the trend of in-vehicle network

Today, as cars gradually develop towards a regional electrical and electronic (E/E) architecture, it is imperative to connect automotive Ethernet to edge sensors and actuators . Ethernet applications are expected to expand from local applications such as smart cockpits to eventually become the backbone of in-vehicle communications.

Single-pair 10BASE-T1S Ethernet is becoming an ideal choice for in-vehicle networks. Ratified in 2019, 10BASE-T1S is one of the newest automotive specifications under the IEEE umbrella. Specifically, the "10" represents the maximum transmission speed (10Mb/s), "BASE" refers to baseband signaling, and "T1" refers to single twisted-pair wiring. The specification is designed to provide a multipoint transmission medium that can handle at least eight transceiver nodes or devices over distances of 25 meters or more . The "S" indicates short length or short range.

10BASE-T1S uses Differential Manchester Encoding (DME) to reduce complexity and cost compared to the pulse amplitude modulation (PAM) signaling used by other automotive specifications . 10BASE-T1S provides faster communication speeds than CAN-FD and the opportunity to eliminate traditional network protocols such as CAN and FlexRay . 10BASE-T1S enables a "full Ethernet" IVN approach to support point-to-point and multipoint transmission. Its multipoint capability is suitable for channels up to 25 meters long and can support up to 8 nodes.

10BASE-T1S greatly simplifies the connection of various sensors and actuators, from seat comfort control to ADAS blind spot detection, with only one PHY ( physical layer interface) per node. The benefit is that it does not require a gateway to convert CAN or CAN-FD to Ethernet, which reduces weight and material costs. Moreover, 10BASE-T1S runs 2 to 3 times faster than the controller area network (CAN) topology, reaching 10Mbps compared to 2Mbps for CAN and 5Mbps for CAN-FD.

It also benefits from using the same software stack as 100/1000BASE-T1 Ethernet. Apart from the different PHYs, no additional gateway is required between the two. With the advent of software-defined vehicle (SDV) architectures, another advantage of Ethernet is that it eliminates the need for a gateway for firmware updates, thus simplifying software management.

Conclusion

The launch of 10BASE-T1S means that automakers have a new standard to adapt to after CAN/CAN-FD. Avnet is working with long-term partner ON Semiconductor to promote the popularization and application of 10BASE-T1S technology. ON Semiconductor will launch the NCV7311 and NVN7410 series chips that support automotive 10BASE-T1S technology this year to provide customers with comprehensive and reliable in-vehicle network solutions. These MAC and PHY transceiver devices will promote the transformation and upgrading of the automotive industry and create a new future of intelligent networking.