How In-Vehicle Networking Bolsters Connectivity on the Road
Key takeaways:
- Both automotive Ethernet and SerDes are quickly evolving toward 100 gigabits per second bandwidths.
- Wireless technologies like Bluetooth, Wi-Fi 6, 5G, and 6G will become essential components of in-vehicle networking.
- Cybersecurity will be a growing concern as software-defined vehicles become the norm on our roads.
The automotive industry is undergoing massive changes. Many societies around the world are moving away from combustion engines and embracing electric or hybrid vehicles. More manufacturers are taking steps toward Level 4 and Level 5 autonomous driving. Customers are increasingly demanding assistance, connectivity, and safety features. Governments are investing in intelligent transportation systems for automated safety on the roads.
In-vehicle networks are the technical foundations that will enable manufacturers to navigate all these changes successfully. In this article, gain an understanding of the different aspects of in-vehicle networking.
What is in-vehicle networking?
In-vehicle networks (IVNs) are the internal communication networks that connect vehicle subsystems internally and to one another so that they can coordinate their functions.
On average, modern vehicles have around 100-150electronic control units (ECUs) that supervise various internal and user-facing subsystems like the:
- powertrain assembly
- emission control system
- battery management in electric vehicles
- braking system
- advanced driver assistance system (ADAS)
- infotainment system
- door and window control systems
- vehicle communication system
- vehicle-to-infrastructure system and the internet-of-things (IoT) components that enable it
Each ECU is connected to several sensors, modules, and actuators that are needed for that subsystem's core functions. The ECUs are also interconnected so that an event in one subsystem (like the ADAS) triggers an action in another subsystem (like braking).
What are the key in-vehicle networking protocols used in modern automobiles?
Many physical networking technologies and communication protocols are used in the automotive industry. We explore some of the popular ones in the sections below.
1. Controller area network (CAN)
Figure 1. CAN bus topology (left) versus automotive Ethernet backbone topology (right)
CAN is a mature and widely used automotive network technology. Below are some of its aspects:
- Uses: CAN is extensively used to manage the powertrain, the chassis (suspension control, for example), and the comfort subsystems (like air conditioning and heating), among others.
- Bandwidth: CAN achieves about 1 megabit per second (Mbps).
- Connection topology: At the heart of each CAN is a two-wire CAN bus. Every node is connected to it through two wires.
- Protocol: Each message on the CAN bus has a unique identifier that describes its type and priority. Identifiers and priorities are decided at system design time and programmed into the nodes. Some identifiers are standardized for compatibility between vendors. A node that wants to communicate some information dumps it as CAN packets on the bus. Since all the nodes are connected to the same bus, every node receives every packet. Each node examines the message identifiers, sometimes even the message payloads, and decides if that message is relevant to it.
- Arbitration: CAN has a non-destructive arbitration mechanism to manage access to the bus if many nodes try to transmit simultaneously. Once a higher-priority message has been transmitted, the waiting lower-priority message is dispatched.
- Signaling: CAN is a binary digital protocol. It uses differential signaling for robustness against noise and electromagnetic interference (EMI) in the harsh environment of a vehicle.
Figure 2. Standard CAN frame
CAN extensions — like the CAN flexible data-rate (CAN-FD) and CAN extended data-field length (CAN XL) — allow higher data rates (2-10 Mbps) and larger data payloads. CAN XL is used for some of the ADAS subsystems.
2. Automotive Ethernet
Figure 3. An automotive Ethernet zonal architecture
Automotive Ethernet adapts Ethernet technologies and protocols for use in vehicles. Some of its notable aspects are as follows:
- Bandwidth: Automotive Ethernet standards provide high bandwidths ranging from 100 Mbps to 25 gigabits per second (as of March 2024). Networks with 100+ Gbps are currently being researched.
- Uses: This high-speed communication network is the ideal backhaul for interconnecting all the other in-vehicle networks. Plus, its high throughputs are ideal for the video infotainment system, ADAS high-resolution camera feeds, and vehicle diagnostics collection.
- Wiring: A notable characteristic of all automotive Ethernet physical layer implementations is the use of a single, unshielded, twisted pair of wires instead of the usual four pairs prevalent in standard Ethernet. This helps reduce the weight of the wiring harness and improves energy efficiency. To maintain signal integrity and robustness against EMI, it uses differential signaling.
- Connection topology: Automotive Ethernet is typically a hierarchical star topology. Each ECU has a network switch that acts as the local hub to interconnect that subsystem's sensors and actuators. Subsystems are interconnected through higher-level switches. Every node can communicate with any other node as if it's a point-to-point connection with the full bandwidth. However, the 10BASE-T1S PHY 10Mbpsimplementation also offers a bus mode because it's designed to replace CAN.
- Performance: Features like audio video bridging and time-sensitive networking have been designed to make automotive Ethernet suitable for various real-time applications.
3. Automotive SerDes
Automotive SerDes is a relatively new high-performance IVN technology. Its characteristics include:
- Uses: SerDes is currently used in the infotainment and back-up camera systems of some high-end cars.
- Higher bandwidth and lower latency: SerDes can already achieve 16-64 Gbps bandwidths and has lower latencies compared to Ethernet. Both SerDes and Ethernet are expected to converge on inter-compatible standards near the 100 Gbps threshold.
- Asymmetric speeds: Unlike Ethernet, which is symmetric, SerDes is designed such that downlinks from cameras or sensors toward ECUs satisfy high-throughput requirements, while uplinks that just transmit commands have low throughputs.
4. FlexRay
FlexRay was designed to replace CAN. It's not being actively developed anymore but is still used by some manufacturers and has the following characteristics:
- Bandwidths: It allows 10 Mbps, which is 10 times faster than the original CAN standard.
- Timing guarantees: FlexRay provides timing guarantees, unlike CAN, making it suitable for real-time critical systems.
- Fault tolerance: FlexRay was designed for better fault tolerance compared to CAN.
- Network topology: FlexRay uses a bus topology by default but also offers a star topology like Ethernet.
5. Local interconnect network (LIN)
LIN is a low-cost and low-speed (a few kilobits per second) IVN. It remains a popular choice for connecting secondary systems like door and light control. Since it's so cost-effective, LIN is unlikely to be replaced any time soon by any other network.
6. Media-oriented systems transport (MOST)
MOST was the preferred network for multimedia features. MOST was designed to transmit audio, video, data, and control information between various devices within a vehicle, such as the head unit, video player, navigation system, radio, and camera systems.
MOST uses a ring network topology, and its bandwidth can range from 25 to 150 Mbps.
However, modern video infotainment systems are migrating toward Gbps-speed automotive Ethernet.
7. Wireless technologies
Some manufacturers and technology providers are researching wireless technologies like BlueTooth, Wi-Fi 6, and 5G / 6G for both in-vehicle networking and external vehicle-to-everything communication.
The benefits of wireless networking are reduced wiring weight, better energy efficiency, less risk of damaged wires with time, and the possibility of upgrading wireless components.
At the same time, interference, variable speeds, and network security are some of the challenges of wireless networking technologies.
What are the challenges of designing reliable in-vehicle networks?
Some common challenges in the reliable functioning of in-vehicle networks include:
- Data rates over long wires: Automotive network wires can sometimes be 10-15 meters long. These unusual lengths as well as higher cable attenuation through insertion loss at higher frequencies means that simply increasing the non-return-to-zero signal frequency is not enough to increase the data rate.
- Effects of phase-amplitude modulation (PAM) on signal integrity: PAM, used in both automotive Ethernet and SerDes, increases the signal-to-noise ratio.
- Wiring weight: The wiring harness over its entire length can weigh several dozens of kilograms, increasing the vehicle's weight and reducing energy efficiency.
- Wear and tear: Networking wiring and switches are generally not replaceable. They must endure the 11-12 years for which vehicles are used under different conditions.
- Electromagnetic interference: In-vehicle networks must be robust against the noise and EMI that are prevalent inside a vehicle. Electromagnetic compatibility is essential for automotive networks.
How does in-vehicle networking contribute to advanced driver assistance systems and autonomous driving?
In-vehicle networking is essential for autonomous driving and assistance systems:
- High-resolution sensors like cameras, radars, and lidars — which are critical for driver assistance and especially for autonomous vehicles — are connected using high-bandwidth, low-latency networks like CAN XL, FlexRay, SerDes, and Ethernet so that the data can get to the onboard computers as quickly as possible.
- If a vehicle requires manual takeover upon sensing a complex traffic situation, its sensor ECUs alert the driver in real time over the in-vehicle networks.
- The actuators of the powertrain, cruise control, steering, and braking systems are coordinated over in-vehicle networks to keep the vehicle moving safely at all times under all conditions.
How does in-vehicle networking enable the connectivity and communication features in modern vehicles?
In-vehicle networking enables several connectivity and communication features like:
- Connecting mobile devices to car head units over Bluetooth or Wi-Fi for hands-free driving.
- Sending vehicle diagnostics and road events to manufacturers over cellular networks, which can be helpful for automatically alerting emergency services and helping with vehicle insurance claims.
- Notifying the vehicle's intentions to other vehicles and infrastructure (like street signs) for coordinated safety on the road.
What measures are taken to ensure the security and integrity of in-vehicle networks against cyber attacks?
Some common measures to improve in-vehicle network security include:
- Isolated virtual networks: Mission-critical subsystems are physically and logically isolated from user-accessible subsystems.
- Security or gateway ECUs: These devices focus on in-vehicle cybersecurity, access control, and supervision of critical functions.
- Access control: Implement defense-in-depth techniques with multiple layers of protection around each vehicle subsystem.
- Intrusion detection: Set up intrusion detection and alerting.
- Denial-of-service (DoS) prevention: In-vehicle network traffic and bandwidth usage are monitored to identify DoS attacks early and mitigate them by throttling down or dropping suspicious connections.
Keysight's BreakingPoint software can simulate realistic cybersecurity threats and evasion techniques to harden in-vehicle networks.
How is in-vehicle networking evolving to support the growing demand for electric vehicles and their communication requirements?
The adoption of electric vehicles has coincided with higher levels of autonomous driving and more capable ADAS systems. To support all these changes, in-vehicle networks have been enhanced to support the following capabilities:
- Powerful battery management systems: In-vehicle networks enable the continuous monitoring (both manual and automated) of battery levels as well as automated alerts to ensure occupants' safety under all conditions. Internet connectivity and global positioning enable drivers to navigate to the closest charging station.
- High-resolution ADAS systems: High-bandwidth in-vehicle networks enable the use of a large number of, and a wide variety of, assistance systems like high-resolution cameras, automotive radars, and lidars.
What are some in-vehicle networking standards?
Standardization plays a key role in the development and implementation of in-vehicle networking protocols to ensure that they are compatible across vendors. Some key standards are listed below.
Automotive Ethernet must comply with standards set by the Institute of Electrical and Electronics Engineers (IEEE). Some of its important standards are:
- IEEE 802.3bw for 100BASE-T1 PHY (100 Mbps over a single twisted pair)
- IEEE 802.3bp for 1000BASE-T1 PHY (1 Gbps over a single twisted pair)
- IEEE 802.3cg for 10BASE-T1S PHY (10 Mbps over a single twisted pair)
- IEEE 802.3ch for 2.5, 5, and 10 Gbps automotive Ethernet PHYs
- IEEE 802.3cy for 25 Gbps PHY
- Detailed specifications published by the One-Pair Ether-Net Alliance Inc. (or OPEN Alliance), a collaboration between the automotive industry and technology providers
- IEEE 802.1Qav quality-of-service standards for forwarding and queuing in time-sensitive streams
- IEEE 802.1AS for timing and synchronization
Automotive SerDes must comply with the ASA Motion Link standards designed by an industry alliance group.
Similarly, CAN, FlexRay, and LIN are also standardized, either by international standards organizations or by industry alliance groups.
Keysight delivers your mission-critical in-vehicle networks
In this article, we explored different in-vehicle networking technologies and their characteristics. Keysight's in-vehicle networking design and test solutions provide world-class test equipment and software that enable manufacturers to implement mission-critical IVNs.
Contact us for specialist insights into how you can test and improve your vehicles' capabilities.
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