With the increasing advancement of vehicles, which contribute to improving road safety performance, providing driving assistance functions, and enhancing energy efficiency, the importance of their underlying technologies has also increased. Whether it is traditional internal combustion engine (ICE) driven vehicles, hybrid vehicles, or pure electric vehicles, car design includes dozens of sensors, microcontrollers, and actuators, all of which generate or process large amounts of data.

Modern vehicles are not just a means of transportation, but also advanced computing platforms on the wheels. Like all computing systems, the ability to effectively transmit data is crucial for the smooth operation and secure operation of such systems.

Common In Vehicle Network Technologies (IVN)

Electronic technology has been applied in vehicles for decades, providing many practical functions, usually to enhance safety or entertainment. In the early days, many of these functions existed independently, neither providing data to other systems of the vehicle nor relying on data generated by other systems. However, with the advancement of technology, the advantages brought by integration have gradually emerged, and specialized network technologies for automobiles have emerged.

The commonly used protocols in vehicles include LIN bus (Local Interconnect Network, LIN), CAN bus (Controller Area Network, CAN/CAN-FD), FlexRay bus, and MOST bus (Media Oriented System Transport, MOST). Although each solution has its unique features and can meet different design considerations, more importantly, these existing technical solutions are difficult to meet the growing demands of modern vehicles.

LIN bus is a cost-effective technology that is easy to implement and deploy for low data rate (<20kbps) application scenarios. However, due to its limited bandwidth and the restriction of the number of system nodes to no more than 12, its value in modern vehicles is limited.

The CAN bus (and subsequent iterative versions such as CAN-FD) has been widely used in vehicles and other safety critical systems due to its high stability, reliability, and relative immunity to electrical interference and noise. However, the limited bandwidth (usually around 2Mbps) restricts its use in certain data intensive applications such as entertainment systems and cameras, while also limiting the number of nodes. At present, the new CAN-XL standard is under development to handle higher speeds and have the ability to interface with Ethernet, but for many engineers, transitioning directly to a full Ethernet solution looks more attractive.

The FlexRay bus provides precise timing and synchronization capabilities, making it suitable for time critical applications such as wire controlled drives. However, compared to other methods, complexity limits its popularity.

The MOST bus is only used for information and entertainment systems, and its applicability is limited and its cost is high. Therefore, with the gradual elimination of this technology, it has been replaced by other solutions.

Ethernet is seen by many as an ideal alternative to various existing solutions, providing high bandwidth and low latency communication capabilities. However, the current Ethernet protocol has a problem with its inherent Carrier Sense Multiple Access with Collision Detection (CSMA/CD) mechanism, which means it cannot achieve deterministic operations and is therefore not suitable for any time sensitive application scenarios, such as line controlled drivers. In addition, the cost of Ethernet technology is also a concern. However, considering the enormous potential of Ethernet, deterministic protocols such as 10BASE-T1S have emerged, which include Physical Layer Collision Avoidance (PLCA) mechanisms (see Figure 1), providing the required performance for time critical applications. In addition, the cost of automotive Ethernet devices is rapidly decreasing, allowing more car manufacturers to apply high bandwidth features.

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Figure 1: In the PLCA cycle, before each "slave device" sends data, the "master device" starts communication through a "BEACON" signal to avoid conflicts and related retransmission overhead.

Ethernet continues to develop under the promotion of organizations such as the OPEN Alliance to meet the growing bandwidth demands of modern automobiles. The new standards, such as IEEE P802.3dh, make it possible for fiber optic applications in future vehicles to support highly demanding technologies such as low latency 4K video and augmented reality.

Wireless protocols including Bluetooth, Wi Fi, and mobile communication are commonly used for drivers and passengers to connect their mobile devices. The main demand for wireless communication comes from its ability to perform certain functions, such as tire pressure monitoring (TPMS) and keyless entry (to name just two), in situations where wired connections are not feasible. However, with the development of "V2X" technology, vehicles can communicate with other vehicles and their surrounding environment, and the demand for wireless communication has further increased, but with it comes the need for higher security.

Vehicle architecture

Due to the numerous subsystems and sensors scattered throughout the interior of the vehicle, car manufacturers must carefully choose the vehicle architecture. There are two main options - domain architecture or zone control architecture. The existing domain based architecture combines parts with similar functionalities (such as transmission system, chassis, and comfort) together - although their locations may be scattered across various parts of the vehicle, which requires more wiring and increases weight and cost.

To avoid this problem, many car manufacturers now prefer to adopt a regional control architecture approach, which groups subsystems that are located in close proximity despite having different functions. Therefore, areas such as "right front" and "left rear" can be specified. Although this method reduces wiring requirements, it also increases the amount of data on the "backbone" of vehicle communication between districts, thus requiring higher performance and bandwidth for the in vehicle network.

Normally, each partition is highly integrated with dedicated computing resources, connected to the main CPU through a high-speed (and deterministic) communication backbone network to support real-time applications such as advanced driver assistance systems (ADAS) and line controlled driving. The adoption of regional control architecture provides greater flexibility for the integration, removal, or upgrade of vehicle functions and features. It is easy to expand and adapt to constantly changing needs.

Although regional control architecture may bring many benefits, its implementation can also lead to an increase in the demand for in vehicle network performance. This is mainly due to the need for higher data traffic, low latency, redundancy, scalability support, as well as better security and diagnostic capabilities.

Functional safety

With the increasing level of automation in vehicles, the demand for functional safety and redundancy measures is also growing. More and more systems require compliance with higher ISO26262 Automotive Safety Integrity Level (ASIL), and as drivers increasingly rely on the vehicle's own decisions and actions, safety level requirements are transitioning from A and B levels to more stringent C and D level components. Functional safety covers all design stages from conceptual design to final vehicle retirement.

Undoubtedly, this has a significant impact on the entire vehicle structure and onboard network. Low latency data transmission is crucial for high-performance ADAS functions such as automatic emergency braking and adaptive cruise control. To achieve functional safety compliance, redundant and sophisticated fault-tolerant mechanisms must be deployed on sensors and communication paths.

Although the safety critical functions of all vehicles require time sensitive networks (TSN), the shift towards regional control architecture enhances this demand. Accurate timing adjustment and delay compensation are crucial for ensuring the correct operation of ADAS functions, especially when components such as image sensors, LiDAR modules, and electronic control systems are distributed in different areas of the vehicle. Even when using microphones for noise reduction and other applications in different areas, TSN is required to work effectively. In terms of Ethernet solutions, the existing TSN Ethernet protocol can be reused for automotive applications.

In terms of image sensor and camera interfaces, MIPI CSI-2 (Camera Serial Interface) and DSI-2 (Display Serial Interface) support high-speed data transmission and are ideal choices for transferring large amounts of data between camera systems, displays, and entertainment systems. The Mobile Industry Processor Interface (MIPI) and the Automotive Serdes Alliance (ASA) are further developing a standardized SerDes solution. Ultimately, ASA Motion Connectivity Technology (ASA ML) will be approved for integration with MIPI CSI-2. In this collaboration, research was also conducted on enhancing the security of MIPI protocol and asymmetric Ethernet (high bandwidth transmission, low bandwidth reception) for cameras.

This is reported by Top Components, a leading supplier of electronic components in the semiconductor industry

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Name: John Chen

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