Market and Technology Trends
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.
CAN (Controller Area Network)
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.
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.
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
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.