Satya Bhan
Gtg632v
Low power ZigBee networks for home/building automation
Introduction
The explosion in consumer electronics and industrial automation systems brought to light fairly
quickly the installation costs, inflexibility and clutter of wired networks. In factories riddled with
thousands of sensors such as pressure, temperature and flow meters, besides inbuilt equipment
monitors, bringing all the data back to a central hub for processing has been an engineering
challenge in itself[1]. Moreover the intrusive and costly nature of establishing such a network in
homes thwarted innovations in home automation; now one of the biggest and fastest growing
markets for sensory networks[2]. Over the last decade active research in wireless networks
brought forth numerous networking standards for establishing Wireless Personal Area Networks
(WPAN) such as UWB, Bluetooth, IEEE 802.15 and HomeRF[3, 4]. However the excessive
power consumption of these technologies made them infeasible for use in sensory/automation
networks where the end devices are typically battery powered. To avoid having to replace
batteries in potentially thousands of devices every few months, new low power, low bandwidth
and low cost alternative standards IEEE 802.15.4 and ZigBee were commissioned to improve the
battery life of the end devices to about 2+ years[5, 6]. Furthermore several key features like mesh
networking with stochastic addressing, multiple routing algorithms and asymmetric link
detection were ratified into the ZigBee Pro standard to make deployment of this self configuring
network extremely scalable and easy, eliminating the need for device installers to learn network
architecture, while ensuring a robust and reliable network[2].
Commercial Applications
The ZigBee Alliance identified six application spaces for ZigBee: consumer electronics, PC and
peripherals, residential / light commercial control, industrial control, building automation and
personal healthcare[7].
Home Automation
Although never envisioned as a market for sensory networks, home automation has become the
highest volume shipping application and a major driving force behind ZigBee. Comfort and
safety have been the primary focus of applications designed for the household market[2]. Several
companies such as Phillips, Crestron and AMX have focused on home automation devices such
as lighting controllers and audio/video controllers to make homes energy efficient and
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Satya Bhan
Gtg632v
convenient. Example applications include turning off lights of a room with unoccupied, universal
remote control to centrally manage audio/video equipment, room lighting and other household
appliances. Other products such as Eaton’s Home Heartbeat system are targeted as a home
advisory system with ability to monitor water leaks, small appliance usage, smoke sensors and
doors & windows[2]. The system allows home owners to monitor the status of their homes via
keypads installed in the home and also remotely over the phone. It also allows users to setup
alerts to be sent to their cell phones in case some sensors are tripped. ZigBee allows these
products to be compact, wireless and battery operated making them easy to install; allowing
them to be marketed as do-it-yourself kits.
Building Automation
Originally designed with building automation in mind, ZigBee enables control over the heating
and air conditioning (HVAC), lighting control, and security systems to make buildings energy
efficient. The ease of implementation of mesh network sensors like temperature and occupancy
with high granularity permits a level of control that would be prohibitive with wired systems
especially while retrofitting existing buildings. WiSuite automation is an energy management
system from Riga Development targeted for hotel and motel properties. Using building
occupancy data from the hotels computer system it automatically sets the thermostat of
unoccupied rooms to a power saving level. Other applications include runtime analysis of
building equipment to detect defective HVAC units & fused lights etc with the ability to alert
maintenance instantly via SMS. The energy/time savings from these systems more than offsets
the implementation costs and being wireless makes it easy to reconfigure physical spaces as
frequently required by new tenants[2].
Underlying Technology
The ZigBee Pro standard defines the low bandwidth logical network and applications built on top
of the IEEE 802.15.4 standard physical (PHY) and media access (MAC) layers. It is designed to
operate in the unlicensed bands worldwide with Raw data throughput rates of 250Kbps at
2.4GHz (Global 16 channels), 40Kbps at 915MHz (Americas 10 channels), and 20Kbps at
868MHz (Europe 1 channel)[3]. ZigBee Pro networks are highly scalable and can be
automatically configured in a star or mesh configuration thanks to a stochastic addressing
scheme that randomly assigns an address to new devices from a 16bit address space[2]. The
ability to define both the source and destination addresses in the address field within the MAC
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Gtg632v
allows for peer-to-peer communication within mesh networks and is also used to prevent a single
point of failure of the network[3].
Building Blocks of a ZigBee network
ZigBee networks consist of three device types:
Network coordinator: maintains overall network knowledge and is required to start off the
network. It's the most sophisticated of the three types and requires the most memory and
computing power. It is generally used in non-beacon mode in applications like security systems
where the end sensors sleep 99.99% of the time. Remote units wake up on a regular, yet random,
basis to announce their continued presence in the network. When an event occurs, the sensor
wakes up instantly and transmits the alert. Since the coordinator needs to listen continuously in a
non-beacon mode it is line powered. Beacon mode is more suitable when the network
coordinator is battery-operated. Client units listen for the network coordinator's beacon
(broadcast at intervals between 0.015 and 252s). A client registers with the coordinator and looks
for any messages directed to it. If no messages are pending, the client returns to sleep, awaking
on a schedule specified by the coordinator. Once the client communications are completed, the
coordinator itself returns to sleep[3].
Full function device (FFD): is a network coordinator with additional memory & computing
power and is typically used as a network router or a network-edge device where it communicates
with devices outside of the ZigBee network[3].
Reduced function device (RFD): carries limited (as specified by the standard) functionality to
lower cost, power and complexity. It's generally found in network-edge devices. It is used by
microcontrollers to transmit data collected from the sensors over the network and to receive
instructions to operate an automation control device.
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Satya Bhan
Gtg632v
Works Cited
[1]
[2]
[3]
[4]
[5]
[6]
[7]
Z. Li, "ZigBee Wireless Sensor Network in Industrial Applications," in SICE-ICASE,
2006. International Joint Conference, 2006, pp. 1067-1070.
A. Wheeler, "Commercial Applications of Wireless Sensor Networks Using ZigBee,"
Communications Magazine, IEEE, vol. 45, pp. 70-77, 2007.
M. Galeev, "Home networking with Zigbee." vol. 2007: Embedded Systems Design Embedded.com, 2004. Availible:
http://www.embedded.com/columns/technicalinsights/18902431?_requestid=26912
[Accessed Sept. 6, 2007].
Techweb.com, "WPAN Definition: TechEncyclopedia from TechWeb." Availible:
http://www.techweb.com/encyclopedia/defineterm.jhtml?term=WPAN [Accessed Sept.
6, 2007]
L. Qilian, "A design methodology for wireless personal area networks with power
efficiency," in Wireless Communications and Networking, 2003. WCNC 2003. 2003
IEEE, 2003, pp. 1475-1480 vol.3.
A. Wheeler, "Debugging building automation applications - Building automation has
been hamstrung by the lack of practical and affordable communications technologies but
ZigBee makes it practical to embed wireless communications into virtually any
commercial building automation product," Computing & Control Engineering Journal,
vol. 18, pp. 30-33, 2007.
D. Egan, "The emergence of ZigBee in building automation and industrial control,"
Computing & Control Engineering Journal, vol. 16, pp. 14-19, 2005.
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Satya Bhan
Gtg632v
Team Details:

Team: Team5

Members: Satya Bhan, Andrew Ausley, Michael Moseley

Advisor: Milor, Jay H. Schlag
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