wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

30-10 Industrial Communication Systems
Z-Wave is a wireless (low-power) standard designed to address remote control applications in residential
environments, created by Zensys and standardized by the Z-Wave Alliance [37]. Z-Wave operates in
the 900.MHz ISM band (United States, 908.42.MHz; Europe, 868.42.MHz; Hong Kong, 919.82.MHz; and
Australia/New Zealand, 921.42.MHz), has a 30.m range in open space, and supports data rates of 9600
or 40.kbps. The technology supports a mesh topology in which nodes communicate with each other
directly, when they are in range, or route packets through other nodes, otherwise.
ZigBee is a communication technology designed for low-rate wireless PANs specifying the network
and application layers on top of the IEEE 802.15.4 MAC (and PHY) and encompassing application
profiles that guarantee interoperability among products from different manufacturers. Currently, two
(publicly available) profiles targeting home area networks (HANs) are available: smart energy and home
automation. The first focuses on energy management while the second targets appliance control and
management in smart homes. Further information about this technology can be found in the corresponding
chapter of the book.
Although X10, Z-Wave, and ZigBee protocols were designed envisaging smart home networking
applications, there are other standard technologies that can equally meet the requirements of smart
homes. Examples of these technologies are the CAN fieldbus [38], Bluetooth [39], and IEEE 802.15.4
[40]. The CAN protocol was developed by Bosch, and besides being widely adopted in the automotive
industry, it can be employed in smart/assistive home networking due to its properties and add-ons
related to fault-tolerant operation and real-time communication. Bartolomeu et al. [38] describe a commercial
home automation system that enables severely disabled users to operate enhanced appliances
using custom interfaces. This system is supported in a CAN fieldbus using a producer–consumer communication
model in which enhanced home appliances (e.g., window blinds, doors, lights) are operated
using human–machine interfaces (HMIs) or specific control appliances (e.g., switches). The trigger of a
command results in the transmission of a broadcast message in the CAN fieldbus. Since each message
defines its consumers, only they will accept the command and act accordingly. An extension of this
communication model employing a wireless technology has been studied in [41] where an assessment
of the timeliness of multihop broadcasts in ZigBee networks was conducted. The conclusion was that
producer–consumer communications supported on ZigBee multihop broadcasts are adequate to building
automation systems of reduced size, operating without retransmissions (i.e., in free RF channels).
Dengler et al. [39] employed Bluetooth for supporting sensor/actuator communications in smart
homes. Their approach consists of installing sensor (e.g., temperature, motion, light) and actuator nodes
in specific places around the dwelling so that abnormal events can be detected and properly dealt with.
Sensors and actuators (BTnodes) are enabled to communicate with each other over multiple hops by
a routing protocol implemented on top of the Bluetooth L2CAP layer. This sensor/actuator network
employs a simple proprietary protocol (on top of the routing layer) that comprises three types of messages
handled with different priorities: emergency, command, and data. Emergency messages (calls)
are broadcasted whenever an anomaly is detected and are periodically retransmitted until a handling
confirmation (acknowledgment) is received from an actuator. Command calls are (acknowledged) messages
used to initiate remote processes in sensor nodes (e.g., recalibration). Data calls are periodic unacknowledged
messages transmitted to maintain a chronicle of the environment status, thus allowing
information to be analyzed and/or displayed to users in and outside the smart home. Provided that sensor/actuator
information must be available beyond the smart home (e.g., alarm notifications, real-time
monitoring), Dengler et al. also propose gateways allowing the bridging of the sensor/actuator network
with popular communication technologies, such as Wi-Fi, telephony network, etc.
In [40], Khan et al. present the architecture of a clustered hierarchical home area network (HAN)
supported on IEEE 802.15.4 technology operating in the beacon-enabled (beaconed) mode. Here,
nodes including sensors (e.g., temperature, light, pressure, motion, smoke, humidity) are deployed
in different areas of the house (bedroom, lounge, library, pool, etc.) and grouped in clusters. Sensor
nodes belonging to a given cluster can only communicate with a central node denoted by cluster
head, thus enforcing a star topology at the intracluster level. Cluster heads, on the other hand, can
© 2011 by Taylor and Francis Group, LLC