Networking Vehicles to Everything by Markus Mueck

Author:Markus Mueck
Language: eng
Format: epub
Publisher: De|G Press
Published: 2017-12-10T16:00:00+00:00

4.3Communications

There are two implementation areas where V2X communications has got an impact, intra-vehicle networking and connectivity and outside vehicle networking and connectivity. There is a steadily rising request for data connectivity inside vehicles. The requirements of in-vehicle networking and connectivity are very diverse according to their application area and use cases. Thus, vehicle manufacturers apply networking technologies like the controller area network (CAN), the local interconnect network (LIN) and FlexRay to connect electronic control units (ECUs) with each other.

CAN is currently the de-facto standard protocol for in-vehicle networking with several Mbps bandwidth and non-deterministic behavior under high load. It is widely used in the basic trunk network, in the powertrain and body systems. The current flexible data-rate protocol (CAN FD) delivers communications up to 5Mbit/s and with partial networking (CAN PN) at an improved energy efficiency. LIN is a single-master in-vehicle networking bus protocol vehicle for body applications with 19.2 kbps and a UART interface that is used in switch input and sensor input actuator control. FlexRay is a high-speed, high-performance communications protocol up to 10 Mbps, with flexibility, reliability and security which is mainly used for X-by-wire, ADAS, and high performance applications. And the media oriented systems transport protocol (MOST) is designed for multimedia networking using optical fibre with bandwidth up to 150 Mbps.

For example, the chassis network applies CAN or FlexRay for high data rate, guaranteed response time and high reliability whereas the body electronics network implements CAN or LIN to link a large number of ECUs at moderate data rates and reliability but with low power consumption. The infotainment network applies MOST for multimedia high data throughput. In-vehicle networking and connectivity next-generation technologies include options such as mobile high-definition link (MHL), high-definition multimedia and control over a single cable (HDBaseT), Wi-Fi, near field communications (NFC) and Ethernet which is mainly used for diagnostics today but has high potential for more.

The intra-vehicle and outside vehicle communications technology evolves in stages. In the first stage ECUs get applied independently to various vehicle components like the engine, brakes, steering, etc. and the in-vehicle network is not used. In the next stage each ECU exchanges data for improving the efficiency of the control system and each system operates almost independently. In this stage the timing constraints on vehicle networking and connectivity are loose. With integrated systems in the next stage, each system still operates autonomously, but some applications are provided with multiple ECUs connected with in-vehicle networks. For functional safety the mechanical backup system is still present and the basic functions of a vehicle are well-maintained even if the electronics system fails. In the next stage V2X networking and connectivity are intensively implemented and the mechanical systems get exchanged with ECUs and networks.

The wireless V2X networking and connectivity technology has to fulfill the often contradictory requirements of all vehicular use cases with their extreme complexity of network topologies, mobility, environment dynamics and technology heterogeneity. It has to support unidirectional broadcast and geocast as well as direct communications peer-to-peer in ad-hoc or direct mode with always available coverage.

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