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Basics of Switches and Transceivers in Automotive Ethernet

A quick review of Ethernet switches and transceivers will highlight their importance in the automotive Ethernet and the OPEN Alliance.

By John Blyler, Editorial Director, IoT Embedded Systems

The connectivity that we’ve long enjoyed via the Internet at home and in the office is quickly moving to our automobiles. By 2025, the mobile operators group GSMA predicts that every car will be connected to the Internet. One of the easiest and most cost effective way to implement in-vehicle networking is via the tested and proven Ethernet.

In fact, there is a consortium whose sole aim is to make consumer-level Ethernet capable of meeting the automotive industry’s stringent requirements. The OPEN (One-Pair Ether-Net) Alliance Special Interest Group (SIG) is a special interest group formed by BMW, Broadcom, Freescale, Harman, Hyundai and NXP to establish BroadR-ReachTM as an open standard for automotive connectivity. BroadR-Reach technology is an Ethernet physical layer standard that allows multiple in-vehicle systems to simultaneously access information over unshielded single twisted pair cable.

As in the home and office, switches and transceivers will form the backbone of the automotive Ethernet. Let’s have a quick review on both these devices.

What are Switches and Transceivers?

Switches connect multiple devices – usually computers – together within the same network. They are generally used to expand the capacity of a network by adding more ports. Switches are designed to pass traffic through as quickly as possible, typically to a router which acts as “the brain” of the network.

In the home and small office, an Ethernet switch is typically part of the router. The latest switches support gigabit speeds.

The best switches use Deterministic Ethernet technology to guarantee message latency in applications such as autonomous driving. Deterministic Ethernet refers to a networked communication technology that uses time scheduling to bring deterministic real-time communication to standard IEEE 802 Ethernet. This technology effectively permits time-scheduled traffic to be partitioned from all other network traffic and is therefore immune from disturbance. This means that in a Deterministic Ethernet network, latency of critical scheduled communication is guaranteed.

Further, Deterministic Ethernet supports the trend toward increasing bandwidth requirements of up to one gigabit, while ensuring high reliability in networked control systems and high availability in fail-operational applications.

A transceiver – short for transmitter-receiver – is a device that both transmits and receives analog or digital signals. In a local-area networks (LANs), the transceiver actually applies signals onto the network wire and detects signals passing through the wire. This is all done on the physical layer or PHY. In Ethernet networks, a transceiver is also called a Medium Access Unit (MAU).

For automotive applications, it’s important the transceiver supports low power modes. When the engine is off, the systems must sleep. Meanwhile, the Ethernet PHY stays partially powered, waking up the system only upon activity on the network. Modern Ethernet PHY designs do not require additional components like voltage regulators to stay on while the engine is off, which greatly improves power consumption and battery lifetime.

Figure: Switches (green boxes) and transceivers (orange box) for the backbone of the automotive Ethernet platform. (Courtesy of NXP).

Data and Connectivity

The adoption of Ethernet is quickly accelerating with the rise of secure connected cars and the subsequent high demands for data transport.

“Automakers plan to use in-vehicle Ethernet broadly to enable a variety of applications and functions,” said Thilo Koslowski, vice president and automotive practice leader at Gartner. “These include safety, driver information systems, advanced driver assistance systems (ADASs) and entertainment. By 2023, 162 million Ethernet nodes containing 242 million ports will be included  in produced consumer vehicles, worldwide.”

All of the members of the OPEN Alliance and many more are supporting the adoption of Ethernet technology into tomorrow’s automobile. For example, NXP has shipped six billion CAN, LIN, and FlexRay transceivers to the global automotive industry and two million transceivers are supplied every day. Ethernet will complement these existing standards.

Recently, NXP announced its new OPEN Alliance BroadR-Reach™ product portfolio for the automotive Ethernet: the Ethernet swtich (SJA1105) and low-power transceiver (TJA1100). For more information, check out the follow links:

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