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Automotive Ethernet: The Car's Wired Network

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What exactly is Automotive Ethernet? Simply put, it’s the use of Ethernet technology within vehicles, like cars, to connect various components using a wired network. Think of it as the nervous system of your car’s electronics.

Definition: The ethernet used in automotive vehicles such as cars is known as automotive ethernet . It is a physical network which is used to connect various components within a car using wired network.

This specialized type of Ethernet needs to meet some pretty demanding criteria:

  • High Data Rate, Low Interference: Should support High Data Rate without EMI/EMC problems.
  • Low Latency, Synchronization, and Bandwidth: Should meet latency, synchronization and bandwidth requirements.
  • Power Delivery: Power should be delivered over ethernet cables
  • Distributed Architecture: Should support distributed network architecture for communication
  • TCP/IP Compatibility: Should work with TCP/IP based protocols

Automotive Ethernet

Figure 1 illustrates a typical Automotive Ethernet setup. The Physical Layer (PHY), responsible for transmitting data over the physical cable, needs to be compliant with single twisted-pair cabling. The PHY interfaces with the Media Access Control (MAC) layer through a Media Independent Interface (MII). The higher-level protocols like TCP/IP reside on the System on a Chip (SoC) of the microcontroller.

Why Automotive Ethernet? Overcoming Past Challenges

In the past, standard Ethernet wasn’t suitable for use in cars due to several key limitations:

  • EMI/RFI Issues: Ethernet could not support EMI/RFI requirements with 100 Mbps data rate. RF noise was too much.
  • Latency: Could not meet low latency requirements in microsecond range.
  • Bandwidth Control: It was difficult to control allocation of bandwidth with different stream rate requirements.
  • Synchronization: It was difficult to achieve synchronization between multiple devices.

Standards and Architectures in the Automotive Ethernet Market

Today’s vehicles are packed with sophisticated systems like advanced driver-assistance systems (ADAS), infotainment systems, and more. These systems need to communicate reliably and quickly.

There are multiple proprietary standards for communication in a car between different vehicle components such as analog signals running on wires, MOST (Media Oriented Systems Transport), flexray, CAN, LIN, LVDS and ethernet technologies. Each component in vehicle has its own wiring and communication specifications. To meet vehicle specifications new and modification to existing IEEE standards have been developed such as IEEE 802.3 and 802.1.

Automotive Ethernet Anatomy

Figure 2 shows the evolution of Automotive Ethernet. The following are the anatomies and standards that are commonly used:

  • 100Base-T1: 100 Mbps Ethernet over single twisted pair which is used for automotive applications
  • 1000Base-T1: 1000 Mbps ethernet over single twisted pair
  • IEEE 802.1 Audio/Video Bridging (AVB): specifies priority queueing, time synchronization and traffic shaping to be used in vehicles.

Types of Automotive Ethernet

Here are some common types of Ethernet used in the automotive industry:

  • One Pair Ethernet (OPEN)
  • Energy Efficient Ethernet
  • Power Over Ethernet (PoE)
  • Gigabit Ethernet (GIG-E)