Automotive Ethernet
Origins and motivations
The rise of driver assistance systems (ADAS), connected infotainment, and centralized vehicle architectures has created a bandwidth need that CAN and CAN FD buses could no longer meet alone. As early as 2008, BMW introduced Ethernet into the 1 Series architecture for onboard diagnostics, before Broadcom developed BroadR-Reach technology — a 100 Mbit/s Ethernet running over a single unshielded twisted pair, compatible with existing automotive wiring.
This innovation removed the main obstacle: where office Ethernet required 2 or 4 pairs of cables, BroadR-Reach needs only one — reducing cabling weight by 30% and cost by 80% compared to conventional solutions. In 2011, the OPEN Alliance SIG consortium was founded to standardize this technology, bringing together BMW, Broadcom, Freescale, Harman, and NXP.
Standards and bit rates
Automotive Ethernet is based on a family of IEEE 802.3 standards adapted for automotive constraints:
| Standard | Name | Bit rate | Cable | Typical usage |
|---|---|---|---|---|
| IEEE 802.3bw | 100BASE-T1 | 100 Mbit/s | 1 twisted pair (UTP), 15 m | Cameras, sensors, diagnostics |
| IEEE 802.3bp | 1000BASE-T1 | 1 Gbit/s | 1 twisted pair (STP), 15–40 m | ADAS, backbone, infotainment |
| IEEE 802.3ch | MultiGBASE-T1 (2.5GBASE-T1, 5GBASE-T1, 10GBASE-T1) | 2,5 / 5 / 10 Gbit/s | 1 twisted pair (STP), 15 m | High-performance backbone, sensor fusion |
| IEEE 802.3cy | 25GBASE-T1 | 25 Gbit/s | 1 twisted pair (STP), up to 11 m | Zonal backbones, uncompressed camera streaming |
| IEEE 802.3cz | Optical (MMF) | up to 50 Gbit/s | Glass optical fiber, up to 40 m | Next-generation optical backbone |
| IEEE 802.3cg | 10BASE-T1S | 10 Mbit/s | 1 pair, multi-drop (bus) | CAN replacement in simple zones |
All these BASE-T1 variants belong to SPE (Single Pair Ethernet): they carry Ethernet over a single twisted pair, instead of the two or four pairs used by office Ethernet. This is what makes the technology compatible with automotive constraints on weight, space and cabling cost.
The IEEE 802.3bu standard adds PoDL (Power over Data Line): the node is powered over the data pair itself, along the lines of PoE but adapted to SPE. A sensor or an actuator then needs only a single cable for both data and power.
Beyond copper, IEEE 802.3cz brings automotive Ethernet over glass optical fiber (up to 40 m), inherently immune to electromagnetic interference on the link. The OPEN Alliance (TC7 group) extends the standard with automotive-specific connector interfaces and test procedures.
The 10BASE-T1S standard is particularly interesting: it introduces a multidrop topology (shared bus) similar to CAN, allowing up to 8 nodes to be connected on the same segment. It is designed to replace CAN in areas of the vehicle where CAN bandwidth becomes insufficient, while keeping wiring simple.
Protocol layers
Unlike CAN, which integrates its own arbitration and error-checking mechanisms, Automotive Ethernet relies on the standard TCP/IP stack, supplemented by protocols specific to automotive:
- SOME/IP (Scalable service-Oriented MiddlewarE over IP) — a service-oriented middleware for inter-ECU communication, defined by AUTOSAR.
- AVB/TSN (Audio Video Bridging / Time-Sensitive Networking) — IEEE 802.1 extensions guaranteeing deterministic latency and precise time synchronization, essential for real-time applications.
- DoIP (Diagnostics over IP, ISO 13400) — a diagnostic protocol that replaces traditional CAN-based UDS for Ethernet-equipped vehicles, enabling much faster data transfers (ECU flashing, OTA updates).
- SecOC (Secure Onboard Communication) — an AUTOSAR security layer for message authentication and encryption.
Fields of application
- ADAS and autonomous driving — cameras, lidars and radars generate massive data streams (up to several Gbit/s) that only Ethernet can carry in real time.
- Vehicle backbone — modern zonal architecture uses Ethernet switches as a backbone, connecting the various domains (powertrain, chassis, body, infotainment).
- Infotainment — high-definition audio/video streaming, smartphone connectivity, multiple displays.
- Diagnostics and OTA updates — Ethernet's high bandwidth greatly speeds up ECU flashing and remote software updates.
- CAN-Ethernet gateway — PEAK-System products such as the PCAN-Ethernet Gateway allow existing CAN networks to be bridged to an Ethernet infrastructure.
Coexistence with CAN
Automotive Ethernet does not replace CAN but complements it. In a modern vehicle architecture, each technology occupies its own niche:
| Criterion | CAN / CAN FD | Automotive Ethernet |
|---|---|---|
| Bit rate | 1 Mbit/s (CAN) / 8 Mbit/s (CAN FD) | 10 Mbit/s to 50 Gbit/s |
| Topology | Bus (native multidrop) | Point-to-point (except 10BASE-T1S) |
| Determinism | Native (CSMA/CA arbitration) | Via TSN (IEEE 802.1 extensions) |
| Cost per node | Very low | Higher |
| Usage | Sensors, actuators, control | Cameras, ADAS, backbone, diagnostics |
Our Automotive Ethernet products
We distribute the PAE range (PEAK Automotive Ethernet), designed for SPE:
- PAE-Media Converter — converter between standard Ethernet (RJ45) and Automotive Ethernet 100BASE-T1 / 1000BASE-T1, to connect a test PC to an in-vehicle network.
- PAE-Cable H-MTD and PAE-Cable MATEnet — SPE cables for the two main automotive connector standards.
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