What are car communication networks?

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Modern vehicles are equipped with complex communication networks, which allow components to "talk" to each other in order to operate in a co-ordinated way. These automotive communication networks are essential for the proper functioning of safety, performance and comfort systems. In this blog we explore basic principles of car communication networks, we will discuss the different topologies used and we will add technical data and case studies to illustrate their applicability in modern vehicles.

1. What are car communication networks?

Automotive communication networks allow the exchange of information between different electronic modules in a vehicle, also known as ECUs (Electronic Control Units). These units control components like the engine, brakes, infotainment system and more.

Essentially, a car communication network works like a nervous system for the vehicle, carrying signals and commands between its essential modules.

Main components of a car communication network:

  • ECUs: Controls critical vehicle functions.
  • Communication bus: The physical connector or "path" on which data travels between ECUs.
  • Communication protocol: Rules governing information exchange between modules (e.g. CAN, LIN, FlexRay).

2. Most common types of car communication networks

a. CAN (Controller Area Network)

CAN is the most widely used communication protocol in vehicles due to its ability to handle large numbers of ECUs with fast response time and high reliability.

Technical data CAN:

  • Transfer speedUp to 1 Mbps.
  • Topology: Bus network - all ECUs are connected to the same bus.
  • Cable lengthUp to 40 metres at 125 kbps.
  • Use: Engine control systems, ABS, airbags.

CAN case study:

A classic example of the use of CAN is in a ABS braking system. The ABS ECU communicates with each wheel's speed sensors and, when it detects a loss of traction, sends commands via CAN to adjust the brake pressure at each wheel, preventing wheel lock-up.

b. LIN (Local Interconnect Network)

LIN is a communication protocol used for simpler systems that do not require fast or complex data transfer. It is mainly used for applications such as the control of electric mirrors, seats and lights.

LIN technical data:

  • Transfer speed: up to 20 kbps.
  • Topology: Master-slave network - the main (master) ECU controls communications with the slave ECUs.
  • Cable length: up to 40 metres.
  • Use: Non-critical applications such as comfort systems.

c. FlexRay

FlexRay is a high-speed network used mainly for critical applications that require low latency and fast data transmission. It is commonly used in advanced control systems such as those for autonomous vehicles.

FlexRay Technical Data:

  • Transfer speedUp to 10 Mbps.
  • Topology: Bus, ring or star network - allows redundant communication.
  • Cable lengthup to 24 metres.
  • UseAdvanced control systems such as active suspension or engine control in autonomous vehicles.

d. Ethernet Auto

In modern vehicles, Auto Ethernet is used to meet the growing need for fast data transfer. It is particularly important for infotainment systems and high-resolution cameras used in driver assistance systems (ADAS).

Technical specifications Ethernet Auto:

  • Transfer speedUp to 1000 Mbps (1 Gbps).
  • Topology: Bus or ring network - similar to Ethernet used in computer networks.
  • Cable length: Up to 100 metres.
  • Use: infotainment systems, parking assistance cameras, autonomous vehicles.

3. Common topologies of automotive communication networks

a. Bus topology

How it works: All ECUs are connected to a single data line (bus) and information is transmitted along this line. Example: CAN networks use this topology to transmit data between ECUs.

Benefits:

  • Efficient cable utilisation.
  • Easy to implement.

Disadvantages:

  • Single data line limitation, which can lead to congestion if there are too many ECUs.

 

b. Ring topology

How it works: The ECUs are connected in the shape of a ring, and data flows in one direction along the ring. Example: FlexRay can use this topology to ensure data redundancy.

Benefits:

  • Redundancy: if a connection fails, data can be redirected.
  • Suitable for critical applications.

Disadvantages:

  • More complicated wiring.
  • More expensive to implement.

c. Star topology

How it works: All ECUs are connected to a central node that manages data traffic. Example: Auto Ethernet uses this topology to handle large volumes of data.

Benefits:

  • Efficient data handling at high speeds.
  • Easy to isolate faults.

Disadvantages:

  • It requires a central node, which increases complexity and costs.

4. Case studies: Real applications of automotive networks

Advanced braking system with CAN and FlexRay

In high-performance vehicles, ABS and ESP braking systems use CAN to communicate between ECUs in real time. But for autonomous vehicles or those with advanced stability control systems, FlexRay provides minimal latency and redundancy, enabling ECUs to make precise brake adjustments in real time, depending on road conditions and driver behaviour.

5. The future of automotive communication networks

As vehicles become increasingly connected and complex, automotive communication networks will need to handle larger volumes of data, with higher speeds and increased reliability. This is why Auto Ethernet is becoming an increasingly important technology, especially for autonomous vehicles.

 

Automotive communication networks are essential for the smooth operation of modern vehicles, and the topologies used, such as CAN, LIN, FlexRay and Ethernet, enable vehicles to manage data efficiently. Each network has its own advantages and disadvantages and their applicability depends on the specific needs of the vehicle. As technology advances, we can expect continuous improvements in the speed and reliability of automotive networks.

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