In-vehicle networking technology is the backbone of every electrical feature in today’s vehicles. The automotive industry, together with technology providers and standardization bodies, has developed specialized communication protocols or made extensions to existing standards to meet the demanding requirements of the automotive domain. Nowadays most of these networking solutions are standardized and maintained by standardization bodies like ISO, IEEE or SAE.
As application requirements have evolved to leverage advances in mobile computing and automation, the protocols supporting these applications have been forced to develop and expand accordingly. When CAN was invented by Bosch, bitrates of 500kbps and 8 bytes payloads were sufficient. Today, with very similar technology, CAN-XL supports transmission speeds of 10Mbps and payloads up to 2KBytes.
Increasing numbers of ECUs and an explosion in vertical information exchange have also changed the way in which ECUs are logically organized. From a vertical approach where ECUs are organized by function, vehicle computing architectures are changing to cluster ECUs by physical location, with an increasing amount of computation moving into central car servers or computing clusters. Such re-organization is made possible by the advances in underlying communication technologies.
Renesas is committed to supporting our customers in developing energy and cost-efficient solutions supporting these new technologies.
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Communication Speeds of Automotive Network Protocol
CAN (Controller Area Network)
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CAN Market Penetration
CAN is the most commonly used protocol for low- and medium-speed automotive control applications. Originally specified for a transmission speed up to 1Mbps and 8 bytes of payload data, CAN FD (Flexible Data-Rate) was introduced to increase maximum transmission speeds with 64 bytes of payload. Standard CAN transceivers support bitrates of 2Mbps, and even 4Mbps under favorable conditions. To enable 4Mbps and higher, special "signal improvement" transceivers are required. The theoretical maximum speed of 8Mbps is achievable under specific operation conditions, whereby in 5Mbps are achievable under typical automotive conditions. CAN-FD is backward compatible to CAN 2.0 (also referred to classic CAN). Many Renesas MCUs and SOCs include a unique CAN macro supporting all required CAN functions and including unique add-on features.
Due to ever-increasing demand in transmission speed and data throughput, the CAN protocol is again undergoing enhancement, to support transmission speeds up to 10Mbit/s and up to 2048 bytes of payload. This enhanced version of CAN is named CAN-XL and is fully backward-compatible to CAN FD.
However, the increase in protocol feature scaling is not entirely in the upward direction. In 2020 a new CAN-related special interest group was formed, focusing on the market for small, intelligent sensor/actuators. The result is a "cut down" version of CAN FD, specified under the name "CAN FD light". Such small endpoints and sub-networks do not require the full robustness and fault tolerance of the CAN feature set. CAN FD light is aimed at small, energy-efficient, economical implementations.
Renesas is committed to actively supporting all this protocol development in the standardization bodies and to providing embedded solutions in future automotive products. Backward compatibility is key in such a protocol family and supported by CAN implementations from Renesas. Even the product which supports the most recent CAN standard is still capable of operating in a classical CAN mode. Upward compatibility is maintained as specified by the standard.
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Mixed CAN Topologies
Ethernet
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Ethernet Product Line-up
In the early 2000s, Ethernet was introduced to the automotive industry for On-Board Diagnostics (OBD) and audio/video applications. Applications in the audio/video domain require advanced Quality of Service (QoS) mechanisms in the Ethernet endpoints. These requirements are defined in a set of specifications developed by the Institute of Electrical and Electronics Engineers (IEEE), and are known collectively as Audio Video Bridging (AVB). The AVB Ethernet macro from Renesas provides hardware support and software-assistance features and is implemented in many automotive MCUs and SOCs.
Another advancement in Ethernet technology that has expanded its use in automotive environments is the development of full-duplex physical layer technology consisting of a single twisted pair. This robust physical layer started with support for 100Mbps and meets demanding automotive requirements. Today, transmission speeds are supported all the way from 10Mbps up to several Gigabits.
As with CAN, the scaling in recent years has not followed a strictly upward trajectory, and efforts have been underway to "fill the gaps" between the lower-throughput protocols and the faster technologies now coming to market. In parallel to development targeted to achieve automotive-compliant transmission speeds for multi-gigabit interfaces, a special technology for automotive with 10Mbps speed is available. The standards have been developed by the IEEE, as it owns the 803.3 physical layer specifications for Ethernet, with support from the OPEN Alliance for specialized automotive specifications.
Aided by this technology, control and Advanced Driver Assistance System (ADAS) functions can be realized, connecting cameras and other sensors, actuators, and data processing ECUs to a switched Ethernet network. To achieve low latency and QoS requirements of automotive applications, IEEE has enhanced the AVB specification set and published it under the name TSN (Time Sensitive Network). The TSN specifications provide tools to achieve bounded latency and reliable networks. Renesas has TSN endpoint and TSN Switch solutions that provide rich feature sets, to build these advanced Ethernet networks efficiently.
LIN (Local Interconnect Network)
Local Interconnect Network (LIN) is a vehicle network protocol, managed by a single master, that achieves a superior cost-performance ratio. It is used in switch/sensor input monitoring and in actuator control. Renesas offers optimized LIN MCUs for diverse body control applications with a variety of packages, low power consumption, operation at high temperatures, and excellent EMI/EMS performance.
In-Vehicle Network Architecture
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Network Architecture Evolution
New communication protocols, higher bandwidth demands, new applications, more complex communication matrices: all of this impacts the network architecture requirements.
Historically, in-vehicle networks were organized into logical domains, such as "Body", "Chassis", and "Powertrain". These domains were interconnected through a central gateway. In the future, the concept of specialized ECUs for domain-specific functions will continue, but the general trend is moving toward separation according to physical location (Zones) rather than by logical function. Zone ECUs connect via high-speed networks to a central ECU where much of the processing is done. These ECUs face several challenges. In the past, ECUs supported only CAN and LIN interfaces with relatively low-speed traffic. There was already the need to bridge between different CAN channels or between CAN and LIN, but these bus speeds range only from 20kbps up to 10Mbps. In addition, these protocols generate event rates and data that can be handled by current real-time processors such as the RH850. Ethernet, on the other hand, adds new orders of magnitude to the required throughput demands. Transmission speeds of 10Gbps and data lengths on the order of kilobytes are major concerns, as newer, faster networks still need to connect to low-speed buses, while protocol conversion is performed in the background. Renesas is addressing this challenge with new SOC concepts and IP components.
To prototype and evaluate such systems, Renesas has developed a multi-gateway evaluation kit called Vehicle Computer which is now available in its third generation.
Renesas IVN demonstrator for Time Sensitive Networking with seamless redundancy
This Demo is featuring a unique development kit as multi-gateway solution for all major automotive communication Interfaces.
Automotive ethernet will become a game changer for the next generation of vehicles and mobility. Exponential growth in bandwidth together with a quality of service allows innovative new architectures to improve comfort and safety and to pave the way to a highly assisted and finally the fully autonomous car. Have a look to our demonstrator showing different network configurations, the effect of link failures to it, and finally countermeasures that could be taken to increase the quality and availability of the network traffic in a real vehicle.
Video Transcript
UWE SCHAEFER: In a world switched on, Automotive Ethernet will become a game changer for the next generation of vehicles and mobility. While CAN has dominated the car network for nearly decades, we face a revolution for the in-vehicle architecture and moving to Ethernet-based networks. Exponential growth in bandwidth, combined with quality of service, allows innovative new architectures to improve comfort and safety in order to pave the way to a highly assisted and finally, the fully autonomous car.
THORSTEN HOFFLEIT: With our partner CETITEC, we have developed this evaluation platform called Vehicle Computer 2. It represents a multi - gateway solution that supports all major automotive communication interfaces, covering LIN, CAN, FlexRay, MOST, and Automotive Ethernet, and allows flexible routing between all of them.
The box is equipped with the powerful Renesas R-Car H3 SoC, the RH850 /F1K microprocessor, and an FPGA based implementation of an Ethernet TSN switch. With these components, the box provides the most common automotive interfaces in a robust housing. The box can be used by OEMs, Tier1’s for evaluation, prototyping, or data logging, and expands the existing toolkits with automotive specific requirements.
Due to the variety of interfaces, many use cases are possible. Central Gateway, Zone ECU, or Central Computer are just a few examples.
UWE SCHAEFER: In order to demonstrate this technology and to showcase the features of deterministic Ethernet, we developed a demo based on the VC2 in an in-vehicle network with a zone-based architecture. The demo consists of five gateway ECUs that are connected by Automotive Ethernet and CAN FD in different network structures, such as ring, star, or mesh. A centerpiece of the demo is the ability to operate the IEEE 802.1 CB standard for frame replication and elimination for redundant communication.
These simple RC type model cars have been equipped with front cameras that send the live stream from the driving track to the front zone ECUs using wireless technology. These ECUs forward the video to the central ECU for track detection, path planning, and driving control. The steering and driving commands are then sent by the rear zone ECUs to the RC control of the model cars. With disabled frame replication mode, any failure on a link will immediately stop the car in operation. Now, after enabling frame replication, the cars move on, because the existing links between the boxes will use both directions. Mesh mode offers more redundant links between the boxes. Such configuration tolerates more link failures. Finally, a mixed network with CAN FD and Ethernet also covers network diversification, which is an important element for functional safety. The backup for control traffic is covered by CAN FD. So even with failures on both Ethernet links, the actuation control is still in operation.
Thank you very much for your attention. I hope to see you soon on a live event from Renesas.
