Vehicle Networking Solutions
Dec 20, 2022 View: 265
Market and Technology Trends
In-vehicle networking technology is the backbone of all vehicles' electrical functions. The automotive industry has joined forces with technology providers and standardization bodies to develop specialized communication protocols or to extend existing standards to meet the demanding requirements of the automotive sector. Today, most networking solutions are standardized and maintained by standardization bodies such as ISO, IEEE, or SAE.
As application requirements evolve with advances in mobile computing and automation, the protocols that support these applications must evolve and expand accordingly. When Bosch invented CAN, a 500kbps bit rate and an 8-byte payload were sufficient. Today, CAN-XL uses very similar technology, supporting 10 Mbps transfer rates and 2-kilobyte payloads.
The increased number of ECUs and the explosion of vertical information exchange have also changed how ECUs are logically organized. In terms of a vertical approach to organizing ECUs by function, vehicle computing architectures are shifting to clustered ECUs by physical location as more and more computing volume moves to a central automotive server or computing cluster. Advances in underlying communication technologies are making this reorganization possible.
NEVSEMI is committed to helping customers develop low-energy and low-cost solutions that support these new technologies.
CAN (Controller Area Network)
CAN is the most common protocol in low and medium-speed vehicle control applications. Originally specified for transmission speeds up to 1Mbps and 8-byte payload data, CAN FD (Flexible Data Rate) is designed to increase the maximum transmission speed with a 64-byte payload. Standard CAN transceivers support bit rates of 2Mbps and even 4Mbps under favorable conditions. To achieve rates of 4Mbps and higher, special "signal improvement" transceivers are required. A theoretical maximum speed of 8Mbps can be achieved under certain operating conditions and up to 5Mbps under typical automotive conditions. CAN-FD is backward compatible with CAN2.0 (also known as Classic CAN). Many NEVSEMI MCUs and SOCs include a unique CAN macro that supports all required CAN functions and contains unique additional features.
Due to the increasing demand for transfer speeds and data throughput, the CAN protocol has been enhanced again to support transfer speeds of up to 10 Mbit/s and payloads of up to 2048 bytes. This enhanced CAN version is named CAN-XL and is fully backward compatible with CAN FD.
However, the increase in protocol feature extensions is not entirely upward. In 2020, a new CAN-related special interest group was formed, focusing on the small smart sensor/actuator market. The result is a "reduced" version of CAN FD named "CAN FD light." Such small endpoints and subnetworks do not require the full robustness and fault tolerance of the CAN feature set. CAN FD light is to achieve miniaturization, energy efficiency, and economy.
NEVSEMI is committed to actively supporting all protocol developments in standardization bodies and will provide embedded solutions in future automotive products. Backward compatibility is key to this family of protocols and is supported by NEVSEMI's CAN implementation. Even products supporting the latest CAN standards will still be able to operate in classic CAN mode. Upward compatibility is maintained as specified by the standard.
Ethernet
In the early 2000s, the automotive industry introduced Ethernet for onboard diagnostics (OBD) and audio/video applications. Applications in the audio/video domain require advanced quality of service (quality of service) mechanisms in the Ethernet endpoints. These requirements are defined in a set of specifications developed by the Institute of Electrical and Electronics Engineers (IEEE), collectively known as Audio Video Bridging (AVB). From NEVSEMI
AVB Ethernet macros provide hardware support and software-assisted functionality and are implemented in many automotive MCUs and SOCs.
Another advancement in Ethernet technology is the development of a full-duplex physical layer consisting of a single twisted pair, thus expanding its use in automotive environments. This robust physical layer started with support for 100Mbps and was able to meet demanding automotive requirements. Today, transmission speeds ranging from 10Mbps to several gigabits are supported.
In the case of CAN, recent expansion has not followed a strictly upward trajectory. There has been an effort to "fill the gap" between low throughput protocols and the faster technologies now available. While the goal is to achieve the development of an automotive-compatible 10 Gigabit interface transmission speed, an automotive-specific technology with a speed of 10 Mbps is also available. These standards were created by IEEE, the owner of the 803.3 physical layer specification for Ethernet, and are supported by the OPEN Alliance for automotive-specific specifications.
This technology enables control, and advanced driver assistance system (ADAS) functions by connecting cameras and other sensors, actuators, and data processing ECUs to a switched Ethernet. To enable the low latency and quality of service requirements of automotive applications, IEEE has enhanced the AVB specification set and released it under the name TSN (Time Sensitive Network). The TSN specification provides tools that enable limited latency and reliable networks. NEVSEMI has TSN endpoint and TSN switch solutions that provide a rich feature set to enable the efficient construction of these advanced Ethernet networks.
Local Interconnect Network (LIN)
A local Interconnect Network (LIN) is a vehicular network protocol managed by a single host and is highly cost-effective. It is used for switch/sensor input monitoring and actuator control. NEVSEMI offers LIN MCUs optimized for various body control applications with multiple packages, low power consumption, high-temperature operation, and excellent EMI/EMS performance.
In-vehicle Network Architecture
New communication protocols, higher bandwidth requirements, new applications, and more complex communication matrices impact network architecture requirements.
Historically, in-vehicle networks have been organized into logical domains such as "body," "chassis," and "drivetrain." These domains are interconnected through a central gateway. In the future, the concept of ECUs dedicated to specific domain functions will continue to exist. Still, the general trend is to separate them by physical location (zones) rather than logical function. Regional ECUs are connected to a central ECU through a high-speed network, where the central ECU does most of the processing. These ECUs face several challenges. In the past, the ECUs only supported CAN and LIN interfaces with relatively low communication speeds. Bridging between different CAN channels or between CAN and LIN has been required, but these bus speeds only range from 20 kbps to 10 Mbps. In addition, these protocols generate event rates and data that can be processed by current real-time processors such as the RH850. Ethernet, on the other hand, adds a new order of magnitude to the required throughput requirements. Transfer speeds of 10Gbps and data lengths in the kilobyte range are major concerns, as newer, faster networks still require connections to lower-speed buses, and protocol conversion is performed in the background. NEVSEMI is addressing this challenge with new SOC concepts and IP components.
To prototype and evaluate these systems, NEVSEMI has developed a multi-gateway evaluation kit called the onboard computer, which is now available in third-generation systems.