Why choose Automotive Ethernet? The evolution of automotive Ethernet technology

The higher the level of the autonomous driving system, the greater the number of independent sensors and the total amount of data generated. Level 2 autonomous driving systems can provide longitudinal and lateral vehicle motion control, allowing the driver to take his hands off and rest his eyes for a while. The system may require the use of 5 RADAR sensors and 5 cameras. Fully autonomous driving systems (Levels 4 and 5) will require up to 20 RADAR sensors and 6 cameras, as well as V2X communication. Forecasts show that an autonomous vehicle will generate about 4 TB of data per day. This data needs to be transmitted, stored and shared on a high-speed, reliable network with extremely short latency, which is the strength of high-throughput, low-latency networks based on automotive Ethernet.

Most traditional automotive serial buses cannot reach the 70MB/s data rate required by LIDAR. When various sensing technologies and wireless communication technologies are integrated, LIDAR, RADAR, cameras, and V2X communications are usually required at the same time. In this case, the amount of data that needs to be transmitted exceeds the existing capacity of traditional automotive serial buses. Therefore, the automotive industry wants to introduce in-vehicle Ethernet to make autonomous driving and advanced ADAS systems a reality.

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Why Automotive Ethernet

Automotive Ethernet is a wired network that connects electronic components in cars. It was designed to meet the automotive industry's requirements for bandwidth, latency, synchronization, interference, security, and network management. IEEE and the OPEN Alliance have developed and maintained the physical layer standards for 100 Mbps and 1000 Mbps automotive Ethernet in the IEEE 802.3 and 802.1 groups.

In the early stages, Ethernet only had a 100Base-T1 1TPCE link from the DLC diagnostic port to the gateway, so it was only used for diagnostics and firmware updates. Figure 1 shows the evolving role of automotive Ethernet as the new backbone (using faster Gigabit Ethernet 1000Base-T1 RTPGE links).

Figure 1: Evolution of automotive Ethernet

In terms of in-vehicle electronic system connection and communication, autonomous driving and ADAS systems, automotive Ethernet has obvious advantages over traditional automotive serial buses. Automotive electronic architecture is becoming more and more complex, with more and more sensors, controllers and interfaces, and requires higher bandwidth, more computers and communication links.

The wiring harnesses connecting these systems are currently the third largest and most expensive component in a car. Today, automakers use a variety of different proprietary standards to provide communications; most components use a single dedicated line or cable. Automotive Ethernet is a unified standard that supports all communications, using a single pair of cables to connect each electronic component to a central network switch.

A joint survey conducted by Broadcom and Bosch shows that by using unshielded twisted pair (UTP) cables and smaller, compact connectors, connectivity costs can be reduced by up to 80% and cable weight can be reduced by up to 30%.

02

The Evolution of Automotive Ethernet Technology

AUTOSAR (Automotive Open System Architecture)

AUTOSAR is an open and standardized automotive software architecture. It is jointly developed by automakers, suppliers and tool developers. AUTOSAR includes the TCP/IP protocol model used in cars. The automotive industry has reached an agreement to establish AUTOSAR as a standard, and automakers will compete on the implementation level of the standard without having to dispute the standard itself. The standard implementation will enable multiple devices to operate seamlessly on a shared network.

Single Pair Ethernet (OPEN)

Broadcom developed BroadR-Reach as a proprietary physical layer standard to support longer distance 100 Mbps copper Ethernet connections. The standard uses Gigabit Ethernet copper technology at the physical layer, including multi-level PAM-3 signaling and better encoding schemes, which reduces the bandwidth required for the cable. It also uses echo cancellers to achieve bidirectional data transmission in a pair of cables. The bandwidth of this standard is 27 MHz, which is smaller than the 62.5MHz bandwidth of the 100Base-T standard, thus meeting automotive EMI requirements. For this reason, the IEEE 802.3 Working Group (802.3bp) formed a group whose task was to define a new standard for achieving 1000 Mbps (1 Gbps) data rate over a pair of twisted pairs. This Gigabit Ethernet physical layer standard is called 1000Base-T1.

Time Synchronization

Some automotive algorithms require multiple sensors to sample simultaneously or use the time at which a measurement is performed as a reference time. Since these measurements are made in different nodes, all nodes in the car must be synchronized with sub-microsecond precision. The IEEE 802.1AS timing and synchronization standard for time-sensitive applications in bridged local area networks has been selected as the synchronization timing standard. This standard uses the profile of IEEE 1588 v2 and introduces a simplified method for faster selection of the master clock.

Time Triggered Ethernet

Some time-sensitive controls require communication delays within 1 microsecond so that the controller can quickly obtain sensor readings or control functions that are extremely time-critical. In traditional Ethernet, data packets must be transmitted one by one, and even at gigabit speeds, it takes hundreds of microseconds to transmit a data packet. The IEEE 802.3br (Interspersed Express Traffic) working group is developing a system to solve this problem, in which high-priority data packets (called Express packets) can interrupt the transmission process of existing data packets and be transmitted first. When it is transmitted, the interrupted data packet continues to be transmitted.

AV Bridging

ADAS relies heavily on timely data from cameras and other sensors. When watching videos on a computer, buffering can be used to solve the problem of unreliable network timing, but this cannot be done for automotive AV systems, which need to control latency and guarantee bandwidth at the same time. The Time-Sensitive Networking Task Force has developed corresponding specifications to support time-synchronized low-latency data streaming services.

03

Comprehensive testing required for successful implementation

Automotive Ethernet engineers need to deal with common high-frequency board design issues including signal noise, signal quality, crosstalk, reflections, impedance matching, and DC power integrity.

To ensure successful implementation and reliable operation, automotive Ethernet also requires comprehensive testing of the physical layer, protocol, conformance, security, and wiring harness.

There are three test points for IoT layer conformance testing (Figure 2): transmitter and protocol triggering and decoding; link segmentation, including wiring harnesses and connectors; and receiver.

Figure 2: Physical layer test points for automotive Ethernet

Transmitter test

Transceiver testing is similar to physical layer characterization solutions for other high-speed digital standards. Engineers must choose a test solution that includes a protocol trigger and decode software package that will provide visibility into data traffic and protocol layer dynamics, saving time in debugging early designs. All required compliance tests need to be pre-packaged in the setup, configuration, and reporting phases so that designers can focus on their core tasks and meet deadlines.

Receiver Test

The powerful 100Base-T1 receiver (RX) compliance test application software should automatically configure all necessary test equipment, simplifying and speeding up the entire test process. The software also provides bit error rate testing (BERT or BER test).

• Simplifies receiver conformance testing

• Automatically configures all required equipment, reducing testing time

• Graphically displays connections to the device under test

• Generates HTML printable pass/fail test reports including margin analysis results

Link segment test

A complete link segment compliance test solution needs to support cable testing, connector testing, communication channel testing, connector crosstalk testing, and crosstalk testing across the entire communication channel.

High-level protocol testing

Automotive Ethernet requires more than just physical layer testing. Validation solutions also require higher-level test methods, including automotive TCP/IP protocol models, time synchronization (IEEE 802.1AS), audio video bridging transport (802.1Qav), and scheduled traffic transport (IEEE 802.1Qbv) protocol implementations. Figure 3 below shows the complete automotive Ethernet protocol model.

Figure 3: Complete model of automotive Ethernet

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Conclusion

Autonomous driving and ADAS will benefit society, but they will also bring many new testing challenges to engineers. At present, the demand for high data rates, bandwidth and data security in automobiles is increasing, and they also require better preparation for future needs. Automotive Ethernet provides the necessary advanced functions and overcomes the shortcomings of traditional automotive serial buses in connecting and communicating in-vehicle electronic systems. Keysight provides high-performance solutions that can help engineers fully test transmitters, link segments, receivers, and higher-layer protocol functions, and ultimately successfully implement automotive Ethernet.