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Proceedings of the Asia-P acific Advanced Network 2010 v. 30, p. 14-21.
http://dx.doi.org/10.7125/APAN.30.3
ISSN 2227-3026
Review of Researches in Controller Area Networks
Evolution and Applications
Wei Lun Ng *, Chee Kyun Ng, Borhanuddin Mohd. Ali, Nor Kamariah Noordin, and
Fakhrul Zaman Rokhani
Department of Computer and Communication Systems, Faculty of Engineering,
Universiti Putra Malaysia, UPM Serdang, 43400 Selangor, Malaysia.
E-mails: [email protected]; {mpnck, borhan, nknordin, fakhrulz}@eng.upm.edu.my
Tel.: +603-89466445; Fax: +603-86567127
Abstract: Initially designed as a new mean in providing communication network
between control units in automotive industries, the controller area network (CAN) has
shown a great surge of interest due to its vast advantages. Since then it is widely used
in various automation industries including military, aviation, electronics, factories and
many others. CAN was designed to allow microcontrollers and devices to
communicate with each other without the presence of a host computer and avoiding
extensive load to the main controller. It is a high performance and high reliable
advanced serial communication protocol which effectively supports distributed realtime control. Ideally, CAN is suitable in application requiring a large number of short
messages with high reliability in rugged environment. These characteristics along with
many others, allows wide opportunity in development of intelligent ubiquitous sensor
network and controller system. This paper presents a brief introduction on CAN
operating principles, its architecture and protocols. Also, various applications of CAN
are introduced and surveyed with more attention given on smart home. Due to its
reliability, efficiency and robustness, an extension of CAN applicants in home
automation is proposed that uses sign language smart controller. Finally, this paper
concludes with a proposed improvement by converting CAN into wireless CAN
(WCAN) by using wireless token ring (WTRP) protocol. WCAN gives a solution
when industrial mobile stations under certain constraints should continue to use CAN
protocol as frame exchange protocol.
Keywords: Controller Area Network; Wireless Controller Area Network; Wireless
Token Ring Protocol.
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1. Introduction
In the past, devices and sensors in automotive industries are connected in a point to point
wiring system which in turn causes the overall network system to be complicated, bulky, heavy
and expensive [1]. In the early 1980s, Robert Bosch GmbH company has developed a new
network controller in the automotive industries with the intention of replacing and simplifying
the wiring system [2]. This development gave rise to a new network system, called the controller
area network (CAN) [3]. The CAN system was developed as a serial bus with high speed, high
reliability, and low cost for distributed real time control applications [4].
CAN is becoming a de facto standard for data transmission in automotive applications [5].
Slowly, CAN begins to gain wide appreciation in various industrial automation due to its high
immunity towards electrical interference and the ability to self diagnose and repair data errors [6]
- [11]. With its low cost, high performances, upgradeability, and providing flexibility,
researchers begin implementing CAN in military, aviation, electronics, factories and many other
industries [11].
This paper provides a comprehensive overview of CAN, its architecture, protocols, standards
and some of its implementation in various industries. In Section 2, the CAN basics such as
message format, message identifiers and bit-wise arbitration are explained. The following few
sections will introduce CAN implementation in various automation fields such as automotive
industries. Nevertheless, a novel approach in applying wireless technology that acquires the
properties of CAN is presented. This new method is known as wireless controller area network
(WCAN) which is an improvement of its wired cousin CAN. The proposed WCAN utilizes the
modified wireless token ring protocol (WTRP) as its architecture. This paper is concluded in
Section 6.
2. Controller Area Network (CAN) Protocol
The CAN was defined in International Standardization Organization (ISO) as a serial
communication bus to replace the complex wiring harness with a two-wire bus. Additionally, it
is a multi-master serial bus that broadcast messages to all nodes in the network system. The CAN
system offers a transmission speed of up to 1 Mbit/s with reliable and error detection method for
effective transmission [9].
CAN uses carrier sense multiple access protocol with collision detection (CSMA/CD) and
arbitration on message priority as its communication protocol [9] - [11]. This communication
protocol allows every node in CAN to monitor the bus network in advance before attempting to
transmit a message. When no activity occurs in the network, each node has the same opportunity
to transmit a message. Additionally, this communication protocol allows collision to be solved
using bit-wise arbitration, based on a preprogrammed priority of each message in the identifier
field of a message. This configuration allows messages to remain intact after arbitration is
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completed even if collisions are detected. In order for the arbitration process to be successful, the
logic states need to be defined as dominant or recessive. CAN defines the logic bit '0' as the
dominant bit where as the logic bit '1' as the recessive bit. An example of CAN arbitration can be
seen in Figure 1 when three nodes are assumed to be transmitting simultaneously. This figure is
illustrating CAN arbitration when three nodes start transmitting their start of frame (SOF) bits
simultaneously. Nodes 1 and 2 stop transmitting as soon as they transmit bit ‘1’ (recessive level),
and Node 3 is transmitting bit ‘0’ (dominant level). At these instances, Nodes 1 and 2 enter the
receiver mode, indicated in grey. When the identifier has been transmitted, the bus belongs to
Node 3 which thus continues transmitting.
Figure 1. CAN arbitration.
The ISO standard defined CAN with a standard 11-bit identifier that provides for signaling
rates from 125 kbps to 1 Mbps. This standard is later improved to allow for larger number of bit,
where the "extended" version with 29-bit identifier. The standard 11-bit identifier field provides
for 211, or 2048 different message identifiers, whereas the extended 29-bit identifier provides for
229, or 537 million identifiers [9], [11]. The data format of both standards can be seen in Figure
2.
Figure 2. Frame format of (a) Standard CAN and (b) Extended CAN.
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CAN protocol can be considered as a message-based protocol as messages are transmitted to
all nodes in the network. Therefore, each node receives the messages and decides whether the
message received is to be discarded or processed. Depending on the configuration of the
network, a transmitted message can be destined to either one node or many nodes [9] - [11]. This
has several important consequences such as system flexibility, message routing and filtering,
multicast, together with data consistency [3].
3. Application of CAN
In the automobile industry, it has been successfully realize the data communication between
inner control system and test actuator on many famous vehicle maker using CAN [13]. CAN is
applied in the function of communication controllers that can transmit electric signals to different
controllers in a vehicle system such as signal lamp, audio, air conditioner, communication,
electronic ignition, engine fuel injection, etc. Not only that, CAN has been proven to reduce and
simplify the amount of signal lines and additionally solve many complex and difficult control
problems of modern vehicles such as Automatic Stability Control (ASC) and Automatic Braking
System (ABS) [12], [13].
An example of CAN implementation can be seen in Jaguar's sports car, the XK8, where CAN
links the Engine Control Module (ECM), Transmission Control Module (TCM), Anti-lock brake
(ABS), instruments and driver information (INST) and the J-gate Illumination Module (JGM).
The various control modules using CAN in vehicle is shown in Figure 3. The introduction of
CAN has allowed new opportunities in harnessing standardization and wire reduction, improved
system visibility, less operator intervention in the diagnostics process, reduced diagnostic times,
and improved on-board diagnostics capability [12].
Figure 3. Various CAN control modules in vehicle.
The popularity of CAN due to its many advantages can be seen in its implementation in
various automation applications. Researches uses CAN in home automation, robotics, medical,
military, structural monitoring and many others. In [14], CAN was introduced in the application
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of direct load control programs for residential automation. This system was intended to allow
users to monitor and control the heating and cooling individual loads of their homes offering
flexibility in demand-side participation in deregulated electricity markets. The overall system is
divided into three subsystems as shown in Figure 4, each with their own function; subsystem of
interaction, subsystem of measurement and subsystem of drive. In this case, transmissions of
data are done using CANopen system.
Figure 4. Three subsystems using CAN in home automation.
Figure 5. CAN based fire detection system.
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In [15], Kyung et. al proposed a fire detection system found in most home and offices which
is designed utilizing CAN as its backbone network as shown in Figure 5. By redefining the
message identifier of Extended CAN, it has been determined that the enhanced system surpasses
the conventional one. This is because conventional method perceives a fire based on the increase
of current as the fire causes analog line to short-circuit. However, using CAN, the system can
synthetically judge a fire occurrence by directly receiving fire detection data from multiple fire
detectors.
5. Proposed Wireless Controller Area Network (WCAN)
WCAN is the new adaptation of its wired cousin CAN. The proposed WCAN is utilizing
some of the properties available in WTRP [16] - [19] as its protocol. WTRP is a wireless based
distributed system. Coincidently, these same properties are required in the success of building
WCAN system. The advantages of having distributed MAC are its robustness against single node
failure and its support for flexible topologies that allows node to partially connect to the network
system. Depending on the requirements and the CAN frame format, some modifications are
needed to be done on token frame.
Figure 6 shows the proposed token frame used in the proposed WCAN architecture system.
Frame control (FC) contains a SOF, 29-bit message identifier that is used in Extended CAN, a
remote transmission request (RTR), and a reserved bit that are to be defined in the future. In
addition, the ring address (RA), destination address (DA), and the source address (SA) are added
into the frame to define the direction of the token frame. RA refers to the ring to which the token
frame belongs to. The sequence number is used to build an ordered list of stations or nodes that
present in the ring. An example of ordered list of available nodes in a sample ring can be seen in
Figure 7.
Figure 6. Proposed WCAN token format.
As aforementioned, the proposed WCAN system is a hybrid property between WTRP and
CAN. Therefore, in order for a station or node to win the arbitration and gain access to the
medium, it must first capture the token that is circulating in the ring and place its message
identifier into the FC field. The token is then transmitted out to the next station in the ring based
on the ordered list that the station has. The next station captures the token and examines the
message identifier first. If the message identifier is having the higher priority, the station will
transmit the same token to the next station on the ordered list. However, if the station wants to
transmit a message or information which is in turn having higher priority, it will replace the
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message identifier in the token with its own and transmits it to the next station. A station or node
will only know if its transmission is successful when the token it receives next contains the same
message identifier it has. Otherwise, it will be in receiving mode until it receives the token back
with a lower priority message identifier.
Figure 7. The ordered list of token ring in node D for WCAN system.
6. Conclusion
This paper presents a brief overview of CAN. This network is emerging and gaining high
ground in many applications from automobile industry to automation and factory industries.
CAN is a multi-master serial bus that allows an efficient transmission of data between different
nodes. With its flexibility and robustness against electrical interference, CAN have become one
of the main choices in many researches as the ideal network system. In this paper, a new
approach in transforming the traditional wired CAN into wireless CAN (WCAN) has been
proposed. The proposed WCAN system shares the same properties as can be found in WTRP
protocol with a few modification and adjustment on the token frame. This characteristic gives
rise to easier and more versatile design of an automation system. However, this paper only
concentrates on the basic structure of the WCAN-based system. More experimental and analysis
need to be performed in order for the system to be fully developed and utilized.
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