The transition from traditional automotive point-to-point wiring to in-vehicle networking using industry standards has enabled carmakers to add many new electronic features for comfort, convenience and infotainment, improve control of the chassis and powertrain, and electrify various subsystems to save cost and weight.
Multiple networks using a variety of protocols, coexisting in the same vehicle, can support large numbers of connected nodes. At the beginning of the millennium a typical car may have had just a few networked nodes. This has now risen to over 20, while the number of nodes in some of today's high-end prestige models can exceed 100. Factors contributing to this rapid increase include the use of electronically controlled lighting such as LED lamps for interior and exterior applications, and the adoption of Advanced Driver Assistance Systems (ADAS) such as collision avoidance and pedestrian recognition. Another factor to consider is the effect of hybrid-electric vehicles (HEVs) and micro-hybrid technologies. The integration of regenerative equipment, and electric traction systems in HEVs, further increases connectivity demands within the vehicle.
Multiple Buses, Extra Nodes
Several buses and a variety of protocols are typically used to satisfy the various demands of body-electronics systems, powertrain controllers, infotainment systems and safety-oriented electronics. These include industry standards such as the Local Interconnect Network (LIN) and SAE J2602, Controller Area Network (CAN) and FlexRay. Signals of higher bandwidth, such as body-mounted camera feeds may be distributed using 24.8Mbit/s Media Oriented Systems Transport (MOST) or IDB-1394 (automotive FireWire) operating up to 800Mbit/s. Automotive Ethernet will be a feature in the cars of tomorrow to support high data rate applications and to act as a backbone network connecting different functional sub-networks.
LIN supports data rates up to 20kbit/s, which is adequate for controlling the large numbers of body electronics applications such as window lifters, mirror and headlamp adjusters, seat-positioning mechanisms, and other motors, pumps and fans. LIN supports simple command/acknowledge traffic; intelligence in subsystems such as