I. Development of Automotive Communication and Information Technology

Traditionally, automobiles were mechanical systems. With the development and continuous application of information technology, more and more electronic and information technologies have been used in automobiles. Almost all assemblies and systems have become integrated mechatronic-information systems, and more and more functions and devices based on information technology have emerged. In-vehicle information systems and information technology are among the most important parts of new automotive technologies. Almost all new technology growth points in automobiles are related to electronic technology and information technology. The increasing number of in-vehicle electronic and information systems has given birth to in-vehicle network communication technology. The development of the Internet of Things based on the Internet will inevitably lead to vehicle networking that realizes interconnection between vehicle-to-vehicle, vehicle-to-road, vehicle-to-person, and vehicle-to-service center, making an automobile a mobile network part of the global Internet, as shown in Figure 1-1. With the development of automotive intelligence and the improvement of intelligent control and intelligent perception capabilities, the autonomous working capability of automobiles will continue to improve.

1. Development of In-Vehicle Network Technology

With the continuous development of automotive electronic technology, the number of electronic devices in automobiles is increasing rapidly. As the prices of electronic components decrease, the speed of electronic technology extending to low-end vehicles is also very fast. Now, almost every assembly in an automobile is an integrated mechanical, electronic, and information device. In systems, the role played by electronic and information parts is becoming increasingly important, so much so that some people believe that automobiles are transforming from mechanical systems with a large number of electronic technologies and devices to electronic information systems supported by certain mechanical devices. The continuous increase of electronic information devices in vehicles has caused the electronic circuits connecting these devices to expand rapidly. Therefore, effectively realizing the interconnection of these devices under the condition of continuously increasing electronic devices has become a problem that must be solved. Using the traditional point-to-point parallel connection method obviously cannot escape this predicament, and network structures based on serial information transmission have become an inevitable choice.On the other hand, with the deepening of automotive electronization, Control By Wire (CBW) technology based on network communication will be widely used in automobiles, which is another reason for the demand for network technology. So-called wire control means using electronic information transmission to replace the transmission parts previously connected by mechanical, hydraulic, or pneumatic systems, such as shift rods, throttle cables, steering gear transmission mechanisms, brake oil circuit systems, etc. Wire control technology involves not only changes in these connection methods but also changes in control mechanisms and control methods as well as changes in actuators (electrification). The widespread application of wire control technology will form a completely new automotive structure. Figure 1-2 shows the basic principle of the wire control process. Control intentions are converted into electrical signals through the human-machine interface and transmitted to actuators, which control functional devices; sensors perceive the state of functional devices and transmit electrical signals to the human-machine interface, providing feedback to the driver. Wire control systems need to transmit large amounts of information between human-machine interfaces, actuators, and sensing mechanisms, as well as with other systems. Network technology based on serial communication is the best structure for implementing this communication function. Wire control technology requires networks with good real-time performance and high reliability, and some wire control parts require redundant “function implementation” to ensure that basic functions of the device (assembly) can still be achieved when failures occur (Fail-Operational). Just like current ABS (Antilock Brake System) and power steering, they still have basic braking and steering functions when circuits fail. This requires networks used for wire control to have high data transmission speeds, good time characteristics (the time when communication events occur is deterministic), high reliability, and necessary redundant technology, which are also characteristics of automotive networks.The most fundamental reason for using networks in automobiles is the social demand for computer networks and the interconnection of various things based on such networks. The development trend of interconnected intelligent vehicles under the intelligent transportation system will inevitably make automobiles endpoints or mobile networks on the Internet. In intelligent transportation systems, an automobile should have the function of receiving and providing relevant information, such as receiving positioning signals, providing geographic information services, receiving management information, sending vehicle status information, and making safety service requests. With the trend of intelligent transportation systems toward cyber-physical integration, functions such as remote access to vehicles, remote control, combination of multi-information obtained through networks with vehicle control, and autonomous intelligent operation will also continue to improve. To complete the requirements of these functions, strong communication capabilities, computing capabilities, and data sharing functions are needed, which are also the most basic functions of computer networks. Communication based on computer networks and new technologies and applications based on such capabilities have become one of the most important key technologies for vehicles and are developing rapidly, changing the “genes” of automobiles.Currently, in vehicles, the information service part often shares a network with the on-board media system, namely the media and information network, while the control part has a relatively independent network. With cyber-physical integration, the division of labor in in-vehicle networks is continuously being broken and reorganized, and the carrier networks for information flow and control flow may be integrated.Early in-vehicle networks did not develop their own universal network standards but adopted some existing conventional standards, such as UART (Universal Asynchronous Receiver/Transmitter). Automobile manufacturers also mainly followed the traditional development model of automotive technology, developing network systems based on needs and their own foundations, with little external cooperation and poor openness. Automotive network systems and control and information units applying networks often have multiple different sources, with different specifications depending on regions or manufacturers. However, network technology itself has characteristics that depend on standards. To reduce installation costs and improve the convenience of design and maintenance, it is inevitable to require in-vehicle networks to form and adopt industry standards and cooperate closely with information and electronics industries to form an open structure. As cooperation confidence increases and the benefits generated by cooperation increase, this trend of adopting open standards through cooperation within the automotive industry and with electronic component and information technology companies is becoming increasingly obvious. Products connected to networks in automobiles, such as sensors, actuators, and control units, may come from manufacturers in many different industries. This standardization is beneficial for the integration of products from different component or device manufacturers and is also beneficial for the operability of design, assembly, and maintenance. With unified standards, interfaces can be reserved for devices that do not yet exist or replaceable devices during design, most obviously automotive software interfaces (the current level of embedded system hardware in automobiles is sufficient to support relatively independent software, which should be regarded as a component or assembly in automobiles). This standardization has produced so-called Open Architecture, that is, certain technical standards and recognition and compliance with these standards.In-vehicle networks really began to be applied in vehicles from the 1980s. In the 1990s, body networks and control networks connecting some electronic control units, including fault diagnosis systems, began to be widely used in different vehicle models. The most widely used standards with the richest supporting technologies and components are CAN (Controller Area Network) and SAE J1850. In the 1990s, on-board media networks, wire control system networks, and intelligent transportation system networks were still in their early stages, with network protocols, supporting software and hardware technologies, and components mostly in trial production stages. Some large automotive companies have different choices for network protocol standards for technical reasons and group interest considerations. There are mainly two choices for wire control system network protocols: one is TTP/C (Time Triggered Protocol, SAE Class C, that is, a time-triggered protocol that meets SAE Class C networks), currently Audi, Volkswagen, Honeywell, and Delphi tend to choose this protocol as the protocol standard for wire control networks; the other is FlexRay, which is a protocol that supports both time-triggered and event-triggered access methods. Currently, BMW, Motorola, Philips Semiconductor, Bosch, and GM tend to choose this protocol as the protocol standard for wire control networks. To compensate for the defects of CAN event-triggered access methods in real-time control applications, Bosch also launched TTCAN, a CAN protocol that supports time-triggered access methods. For dedicated in-vehicle media networks, MOST (Media Oriented System Transport) standards have been used in some high-end vehicles.With the continuous increase in in-vehicle electronic control and information devices and information service demands, the demand for better, faster, and more reliable in-vehicle network facilities is also continuously growing. Especially with the application of multimedia information, electronic maps, Internet network information, etc. in automobiles, bus networks can hardly meet the bandwidth and information transmission format requirements. Against this background, in-vehicle network technologies that support multimedia and high data transmission have begun to emerge, with automotive ethernet being a typical representative.Automotive ethernet inherits the advantages of fast transmission speed and strong scalability of Ethernet and has received widespread attention since its introduction. The membership of the “OPEN (One-Pair Ether-Net) Alliance SIG,” a group that promotes the formulation and popularization of automotive ethernet standards, is rapidly increasing.The rapid growth of OPEN Alliance SIG is based on the automotive industry’s increased trend toward using automotive ethernet. Ethernet began to be practically applied in vehicle On-Board Diagnostics (OBD) around 2008. In the future, while improving real-time performance, ensuring safety during failures, reducing costs, and improving data transmission speeds, it will further expand its application scope. The application scope of Ethernet may extend to backbone networks that connect the gateways of various systems such as in-vehicle AV equipment image transmission (information) systems, body systems, control systems, safety systems, and information systems. Currently, some automotive network standards based on Ethernet have emerged and are continuously being improved and deployed, mainly including AVB (Audio Video Bridging) for information and media and TTE systems with good real-time characteristics.The application of in-vehicle networks involves not only hardware connections between various electronic devices in automobiles but also network-related software that must inevitably become part of the software in every control unit. Automotive software systems will soon become a relatively independent part, and their relationship with automobiles (electronic systems on them) will gradually develop into the same relationship as current computer software and hardware systems. On-board application systems will be able to directly call network function service programs and other general service function software (or firmware) in embedded operating systems. Software design in automobiles will be as important in automotive design as engine design, chassis design, or body design.Although in-vehicle network technology has been widely applied, there is still much work to be done for further requirements. Currently, there is no network system that meets the requirements of low cost, very reliable performance, fault tolerance capability, good time characteristics (including real-time performance and deterministic event response time), and good scalability. Due to the great variation in the levels and purposes of in-vehicle network applications, different levels or purposes have greatly different requirements for network performance. Automobiles themselves are very sensitive to price. If high-performance network systems are used to cover low-level applications, the cost is unacceptable. Therefore, automobiles will have multiple network standards at different levels. This determines that automotive networks will be a multi-level interconnected network structure.

2. Development of In-Vehicle Information Technology

In-Vehicle Infotainment systems are software and hardware systems based on computer, satellite positioning, network communication, electronics, and control technologies that provide safety, environmental protection, comfort, and entertainment functions and services for automobiles. They have become components of modern automobiles and play increasingly important roles in automotive engineering and automotive applications.In-vehicle information systems can be divided into four levels, from high to low: customer layer, service layer, communication layer, and in-vehicle layer. Currently, electronic information technology in vehicles is mainly used for vehicle safety systems, network, communication, and navigation systems, mobile multimedia systems, and human-machine interaction systems.(1) Vehicle Safety SystemsBy applying electronic information technology, vehicles achieve high intelligence, greatly improving the safety of vehicle human-machine systems, avoiding accidents, and reducing the degree of injury.

1. Adaptive Cruise Control System: The adaptive cruise control system controls the vehicle and, after setting the desired lower traffic driving speed, uses radar, sonar, or laser beams to scan the road ahead. When necessary, the adaptive cruise control system will automatically reduce throttle opening, downshift, or even apply brakes to maintain safe following distance. The Mercedes-Benz S-Class 2000 model was the first vehicle in the world to be equipped with an adaptive cruise control system, and other companies have since launched their own adaptive cruise control systems.

2. Collision Warning System and Crash Notification System: Its working principle is similar to the adaptive cruise control system, using radar, sonar, and laser beams to scan potential obstacles. When there is a risk of collision, it issues warning signals and takes automatic braking actions. When used in combination with GPS receivers, crash notification systems can also provide precise location information of the vehicle to rescue agencies.

3. Integrated Safety System: This system consists of 50 technologies, including electronic equipment, microcontrollers, sensors, and other technologies and products that have been or will be launched. Relying on advanced electronic technology and integration expertise, this system focuses on all aspects of driving, such as curtain head airbags, seat belt pre-tensioning and over-tensioning devices, adaptive energy-absorbing steering columns, and active knee guards, mobilizing all safety factors on the vehicle to provide comprehensive, full-course protection for vehicle occupants.

4. Stolen Vehicle Recovery System: This technology provides an anti-theft method based on automatic vehicle tracking. Some stolen vehicle recovery systems require vehicle owner authorization to start the transmitter for automatic vehicle tracking, while other systems automatically start the transmitter for vehicle tracking when the vehicle is intruded upon or driven away without permission.

(2) Network, Communication, and Navigation Systems

1. Network and Communication Systems: This system allows drivers to receive network news, emails, and other information through laptop computers and cordless phones without taking their eyes off the road ahead or hands off the steering wheel, and transmits this information to drivers through voice control. People only need to touch the button on the steering wheel to activate it. This in-vehicle network communication can be achieved through two methods: one is reading email text through digital displays, and the other is converting text files into voice files and reading email content in electronic voice. Email replies can be sent in audio file format or converted to text files through voice recognition systems before sending.

2. Electronic Navigation System: The GPS navigation function of the in-vehicle navigation system is outstanding and can help drivers reach their destinations timely and quickly in the complex urban traffic road network. Using multi-layer guided menus, targets can be conveniently selected by region, city, and facility function classification. The navigation system immediately calculates the shortest driving route and displays it as lines on two-dimensional or three-dimensional electronic maps. Once the car starts, the symbol representing the real-time position of the car will automatically travel along the set route. When encountering traffic jams ahead or unexpected situations requiring changes to the driving route, the satellite navigation system will automatically reset and automatically set a new driving route within seconds, restoring navigation function.

3. Real-time Traffic Information Consultation System: The real-time traffic information consultation system is a vehicle navigation device suitable for people familiar with traffic routes. There are various methods for transmitting real-time traffic information. The RDS system that relies on listening to real-time traffic information through audio systems has been around for a long time. Now companies have launched real-time traffic information tracking services on the Internet that can be queried using computers before leaving the office or home. The most advanced real-time traffic consultation system currently under development is where the in-vehicle navigation system sends digital pulse information, either displayed on regional maps or used to calculate other feasible routes.

(3) Mobile Multimedia SystemsMobile multimedia technology is mainly used to develop rear seat entertainment systems. This rear seat audio-visual technology includes full-color screens, gaming devices, DVD players, power supplies, CD players, video recorders, and players. Mobile multimedia technology is also reflected in intelligent wireless products, remote communication equipment, and information processing products, including providing voice recognition systems that support multiple languages, allowing drivers to control intelligent information/entertainment systems without manual operation, freeing up hands to control the steering wheel. It can also integrate Internet functions into vehicles, allowing people to browse the web, send and receive emails, and conduct stock transactions in the car. At the same time, using “plug and play” methods, automotive consumers can conveniently and quickly update their multimedia products and enjoy richer new services.(4) Human-Machine Interaction SystemsThe most classic human-machine interaction system in vehicles is automotive instruments and control systems for various on-board devices. With the continuous improvement of vehicle informatization, both the information obtained by drivers and the ways of obtaining information have changed significantly. Instrument clusters based on various new digital display technologies and new information delivery methods are continuously emerging in vehicles, and control methods have evolved from various switch buttons to touchscreens, voice, and other methods.The high development and superiority of future in-vehicle information technology are reflected not only in in-vehicle functions and in-vehicle software and hardware technology but also in creating entirely new user experiences. Automobiles will become mobile devices rich in various information functions and are another field with broad application prospects for information technology. The development level of information technology and its application status in the automotive industry field determine the position in future global automotive industry competition. In-vehicle information technology will become an important indicator of the overall level of automotive technology and will also become the foundation of intelligent automotive technology.

II. Introduction to In-Vehicle Networks

The Society of Automotive Engineers (SAE) classifies in-vehicle network systems from low to high performance as Class A, Class B, and Class C networks. With the application of navigation, multimedia, and safety systems in automobiles, higher requirements for network reliability and bandwidth have been proposed. Following SAE’s classification method, Class D and Class E networks have been added, as shown in Table 1-1.Table 1-1 In-Vehicle Network Classification

1. Class A networks are mainly applied in situations requiring low prices, low data transmission speed, real-time performance, and reliability requirements, such as door, window, and trunk network systems in body systems. Class A networks are also used as bottom-level local connection buses for some sensor-level and actuator-level applications.

2. Class B networks are used for systems with higher data transmission speed requirements, including some body control systems, instrument panels, low-level real-time control systems, and fault diagnosis systems (OBD).

3. Class C networks are mainly used for systems with high reliability and real-time requirements, such as high-level real-time control systems for engines and powertrains, as well as wire control systems.

4. Class D networks are mainly oriented toward multimedia and navigation system fields. Currently, mainstream protocols for Class D networks include IDB-1394, MOST, and Automotive Ethernet AVB.

5. Class E networks are mainly applied to control systems with higher safety and real-time requirements. Mainstream networks include FlexRay and Automotive Ethernet TTE.

Local Interconnect Network (LIN) is an automotive low-end network protocol jointly initiated in 1998 by automotive manufacturers Audi, BMW, DaimlerChrysler, Volvo, and Volkswagen with component manufacturer Motorola and development tool company VCT (Volcano Communications Technologies). The LIN standard defines not only communication protocols but also development tool interfaces and application software interfaces (APIs). Its goal is to provide inexpensive bottom-level sensor and actuator-level local network standards. The LIN Consortium not only proposes protocol standards but also includes development tools and API standards, providing convenience for automotive design users and providing a model for future automotive network standardization work. LIN’s protocol standards are based on Serial Communication Interface (SCI), with physical layers adapted to automotive fault diagnosis standard ISO 9141, meeting Electro-Magnetic Compatibility (EMC) and Electrostatic Discharge (ESD) requirements in vehicle environments. Parts that traditionally use LIN bus networks are increasingly being replaced by low-speed CAN networks.The CAN standard proposed by Bosch was first widely adopted in European automobiles. Later, automotive companies in the United States and Japan also use it as Class B or Class C in-vehicle networks. CAN is one of the most widely used automotive network standards and is also adopted by many other industries.MOST and Automotive Ethernet AVB are standards oriented toward in-vehicle multimedia system connections. Due to the large amount of data transmitted by media information audio and video, higher transmission speeds (bandwidth) are required compared to control networks in vehicles. Generally, optical fiber or coaxial cables are required as physical layer media, and twisted pairs are also widely used considering cost factors.FlexRay and Automotive Ethernet TTE standards provide time-triggered in-vehicle network standards, which are more suitable for in-vehicle wire control systems in terms of real-time performance and safety.Wireless local communication technology has some applications in automotive body control systems or media systems, such as in-vehicle devices based on Bluetooth technology.Automotive Ethernet retains the characteristics of fast transmission speed and strong scalability of Ethernet. Future automotive Ethernet signal transmission speeds can be increased to 1Gbit/s. In terms of scalability, when supporting TCP/IP commonly used by communication devices and consumer products, connections with external network devices and network services are very convenient in communication and application functions. As protocols continue to improve in automotive application requirements, they will be increasingly used in in-vehicle control and information systems.Due to the variety of vehicle types and the continuous development of in-vehicle network technology, there are multiple standards for network systems applied to vehicles. If aircraft, ships, agricultural machinery, and other independently moving and carrying tools with some common characteristics with automobiles (long-distance movement, relative independence, self-contained power sources) are included, there are no fewer than dozens of network standards. Many of these networks are applied in different fields. For example, CAN is used in automobiles, off-road vehicles, aircraft, and other fields. Table 1-2 shows some network system standards applied in vehicle-type systems.

III. Characteristics of In-Vehicle Networks and Information Systems

Automobiles require safety, ease of use, simple operation, reliable performance, and are sensitive to price. The application environment of automobiles can be harsh, with almost all possible road, electromagnetic, and climate environments being encountered. Based on these usage requirements for automobiles, the following factors should be considered in automotive system design:

1. Temperature range generally required to be -40~125°C.

2. Effects of oil, water, salt spray, dust, and possible chemical corrosive substances.

3. Effects of mechanical vibration, bumping, and impact.

4. Electromagnetic compatibility issues. The system must have the ability to withstand external electromagnetic interference and must not cause electromagnetic interference to the environment (electromagnetic fields in home environments are 3V·m⁻¹, electromagnetic fields in factory environments are 10V·m⁻¹, and electromagnetic fields in automotive environments may be greater than 200V·m⁻¹).

5. Environmental protection issues. Emissions during operation (including sound, light, electromagnetic, oil, and gas) must meet environmental protection requirements, as well as component and vehicle disposal issues when scrapped.

6. Possible failures and misoperations, such as reverse power connection, loose wire ends, short circuits/open circuits, friction, etc., should minimize losses.

7. Protective measures or safety impacts during accidents should be fully considered.

8. Any component must ensure high reliability with a sufficiently small probability of failure within the required service life.

9. Mass production costs.

In-vehicle network systems should also consider the following factors:

1. Electrical and mechanical characteristics of node-to-bus connection headers and the number of connection headers.

2. Evaluation and performance testing methods for network systems and application systems.

3. Fault tolerance and fault recovery issues.

4. Time characteristics of real-time control networks.

5. Safety of network wiring production processes and usage maintenance processes.

6. Addition of network nodes and software/hardware updates (scalability).

7. Communication protocols and information security.