In-vehicle Networking

In-vehicle Networking:
As we all know that in the vehicle all electrical and electronics parts and components were connected through wiring harness to transmit signal / information from one point to another point. In conventional wiring harness system dedicated wires required for each and every signal. For few featured vehicle this system is good and cost effective but when we talk about a vehicle with luxury features, this system become more complex and costly. To avoid that complexity In-Vehicle networking comes in picture which is also known as multiplex wiring.
In-vehicle Networking
 –Connect the vehicle's electronic equipments.
 –Facilitate the sharing of information and resources among the distributed applications.
 –Change the point-to-point wiring of centralized ECUs to the in-vehicle networking of distributed ECUs.
Aims of In-vehicle Networking:
 –Open Standard
 –Ease to Use
 –Cost Reduction
 –Improved Quality
Benefits of In-vehicle Networking:
 –More reliable vehicle
 –More functionality at lower price
 –Standardization of interfaces and components
 –Faster introduction of new technologies
 –Functional Extendibility
 –Decreasing wiring harness weight and complexity
 –Electronic Control Units are shrinking and are directly applied to actuators and sensors

In-vehicle Networking or multiplexing is based on serial protocols. Modern automobile’s protocols are listed below

S.N Protocol Name Speed Use Origin
1 D2B 5Mbit/s High Speed electrical or optical mainly for digital audio Auto
2 MOST 22.5Mbit/s High Speed (audio, video, control) Auto
3 FlexRay 10Mbit/s High Speed x-by-wire, safety-critical control) Auto
4 Byteflight 10Mbit/s High Speed constant latencies, airbag, sear-belt Auto
5 TTP 5~25Mbit/s High Speed real-time distributed/fault-tolerant apps Auto
6 Bluetooth 10Mbits/s High Speed wireless for infotainment equipments Consumer
7 CAN 50-1000kbit/s Low Speed Controls Auto
8 J1850 10.4kbit/s and 41.6kbit/s Low Speed Controls Auto
9 LIN 20kbps Low Speed Controls Auto

 

Protocol Comparison:

 • Class A (<20 kbit/s) : LIN, CAN
 • Class B (50-500 kbit/s) : CAN, J1850
 • MMedia (> 20 Mbit/s) : MOST, Firewire
 • Wireless : GSM, Bluetooth
 • Safety : Byteflight, TTP/C, Flexray

1. D2B (Domestic Data Bus)
–Matsushita and Philips jointly developed
–Has promoted since 1992
–D2B was designed for audio-video communications, computer peripherals, and automotive media applications
 –The Mercedes-Benz S-class vehicle uses the D2B optical bus to network the car radio, autopilot and CD systems
 –The Tele-Aid connection, cellular phone, and Linguatronic voice-recognition application

2. Media-Oriented Systems Transport (MOST)
 –It was initiated in 1997
 –Supports both time-triggered and event-triggered traffic with predictable frame transmission at speeds of 25Mbps
 –Using plastic optic fiber as communication medium
 –The interconnection of telematics and infotainment such as video displays, GPS navigation systems, active speaker and digital radio
 –More than 50 firms—including Audi, BMW, Daimler-Chrysler, Becker Automotive, and Oasis Silicon Systems—developed the protocol under the MOST Cooperative

3. FlexRay
 –FlexRay is a fault-tolerant protocol designed for high-data-rate, advanced-control applications, such as X-by-wire systems (high-speed safety-critical automotive systems)
 –Provides both time-triggered and event-triggered message transmission
 –Messages are sent at 10Mbps
 –Both electrical and optical solutions are adopted for the physical layer
 –The ECUs are interconnected using either a passive bus topology or an active star topology
 –FlexRay complements CAN and LIN being suitable for both powertrain systems and XBW systems

4. Byteflight
 –Developed from 1996 by BMW
 –A flexible time-division multiple access (TDMA) protocol using a star topology for safety-related applications
 –Messages are sent in frames at 10Mbps support for event-triggered message transmission
 –Guarantees deterministic (constant) latencies for a bounded number of high priority real-time message
 –The physical medium used is plastic optical fiber
 –Byteflight is a very high performance network with many of the features necessary for X-by-wire

5. Time-triggered protocol (TTP)
 –It was released in 1998
 –It is a pure time-triggered TDMA protocol
 –Frames are sent at speeds of 5-25Mbps depending on the physical medium
 –Designed for real-time distributed systems that are hard and fault tolerant
 –It is going on to reach speeds of 1Gbps using an Ethernet based star architecture

6. Bluetooth
 –An open specification for an inexpensive, short-range (10-100 meters), low power, miniature radio network.
 –Easy and instantaneous connections between Bluetooth-enabled devices without the need for cables
 –Vehicular uses for Bluetooth include hands-free phone sets; portable DVD, CD, and MP3 drives; diagnostic equipment; and handheld computers.

7. Controller area network (CAN)
 –Was initiated in 1981 and developed by Bosch developed the controller
 –Message frames are transmitted in an event-triggered fashion
 –Up to 1Mbps transmission speed
 –It is a robust, cost-effective general control network, but certain niche applications demand more specialized control networks.

8. The SAE J1850 Standard
 –supports two main alternatives, a 41.6 kbps PWM approach (dual wires), and a 10.4kbps VPW (single wire) approach.

9. Local interconnect network (LIN)
 –A master-slave, time-triggered protocol
 –As a low-speed (20kbps), single-wire
 –LIN is meant to link to relatively higher-speed networks like CAN
 –LIN reveals the security of serial networks in cars
 –network is used in on-off devices such as car seats, door locks, sunroofs, rain sensors, and door mirrors