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IEEE Transactions on Consumer Electronics, Vol. 55, No. 2, MAY 2009
Contributed Paper
Manuscript received November 8, 2008 0098 3063/09/$20.00 © 2009 IEEE
422
A ZigBee-Based Home Automation System
Khusvinder Gill, Shuang-Hua Yang, Fang Yao, and Xin Lu
Abstract — In recent years, the home environment has seen a
rapid introduction of network enabled digital technology. This
technology offers new and exciting opportunities to increase
the connectivity of devices within the home for the purpose of
home automation. Moreover, with the rapid expansion of the
Internet, there is the added potential for the remote control
and monitoring of such network enabled devices. However,
the adoption of home automation systems has been slow. This
paper identifies the reasons for this slow adoption and
evaluates the potential of ZigBee for addressing these
problems through the design and implementation of a flexible
home automation architecture. A ZigBee based home
automation system and Wi-Fi network are integrated through
a common home gateway. The home gateway provides
network interoperability, a simple and flexible user interface,
and remote access to the system. A dedicated virtual home is
implemented to cater for the system’s security and safety
needs. To demonstrate the feasibility and effectiveness of the
proposed system, four devices, a light switch, radiator valve,
safety sensor and ZigBee remote control have been developed
and evaluated with the home automation system.
Index Terms — Home Automation, ZigBee, Sensor Network.
I. INTRODUCTION
In recent years the introduction of network enabled devices
into the home environment has proceeded at an unprecedented
rate. Moreover, with the rapid expansion of the Internet, there
is the potential for the remote control and monitoring of such
network enabled devices. However, the new and exciting
opportunities to increase the connectivity of devices within the
home for the purpose of home automation remain largely
unexploited.
A. Existing Home Automation Technologies
There are many definitions of home automation available in
the literature. [1] describes home automation as the
introduction of technology within the home to enhance the
quality of life of its occupants, through the provision of
different services such as telehealth, multimedia entertainment
and energy conservation.
There has been significant research into the field of home
automation. The X10 industry standard, developed in 1975 for
communication between electronic devices, is the oldest
standard identified from the author’s review, providing limited
control over household devices through the home’s power
lines. Recently, research into the field of home automation
K. Gill, S. H. Yang, F. Yao and X. Lu are with the Computer Science
Department, Loughborough University, Loughborough, England, LE11 3TU
(e-mail: s.h.yang@lboro.ac.uk).
has continued to receive much attention in academia. [2]
developed a Java based home automation system. An
embedded board physically connected all the home
automation devices and, through integration with a personal
computer (PC) based web server, provided remote access to
the system. The use of Java technology, which incorporates
built-in network security features, produces a secure
solution. However, the system requires an intrusive and
expensive wired installation and the use of a high end PC.
[3] introduced a Bluetooth based home automation system,
consisting of a primary controller and a number of Bluetooth
sub-controllers. Each home device is physically connected
to a local Bluetooth sub-controller. The home devices
communicate with their respective sub-controller using
wired communications. From the sub-controller all
communications are sent to the primary controller using
wireless communications. It is desirable for each home
device to have a dedicated Bluetooth module. However, due
to the fiscal expense of Bluetooth technology, a single
module is shared amongst several devices. This architecture
reduces the amount of physical wiring required and hence
the intrusiveness of the installation, through the use of
wireless technology. However, the architecture does not
completely alleviate the intrusiveness of the installation due
to the incorporation of some wired communications.
Moreover the sharing of a single Bluetooth module between
numerous devices has the disadvantage of incurring an
access delay. [4] introduced a phone based remote controller
for home and office automation. The system differs in that
all communications occur over a fixed telephone line and
not over the Internet. The system can be accessed using any
telephone that supports dual tone multiple frequency
(DTMF). The disadvantages of this system are threefold:
users are not provided with a graphical user interface, users
have to remember an access code, and they have to
remember which buttons to press for the control of
connected devices. [5] proposed a novel control network,
using hand gestures. The controller uses a glove to relay
hand gestures to the system. The problem with the system
lies in the inaccuracy of hand gestures, with the potential for
normal arm movements being inaccurately interpreted as
commands. Moreover, there is the risk of user fatigue if
repetitive hand gestures are required.
The introduction provides a short review of the existing
academic research into home automation. The publically
available research into home automation lies predominantly in
the academic arena, with little industrial research being
publically available. The adoption of home automation
technologies into commercial systems has been limited, and
where available consumer uptake has been slow.
The aforementioned systems offer little in the way of
interoperability. Attempts have been made to provide network
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K. Gill et al.: A ZigBee-Based Home Automation System
423
interoperability and remote access to home automation
systems through the development of home gateways. [6]
defined a home gateway as the point of ingress between a
personal area network and a public access network. They
developed a web server based home gateway to interconnect
IEEE1394, with a power line based home automation system,
and the Internet. To make the system more attractive to home
owners, a real time AV transcoding capability was included.
The system offers an insightful look into the development of a
home gateway; however, the use of power lines as the
communication medium limits the positioning of devices
within the home to areas in close proximity to power sockets.
[7] proposed a home energy management focused home
gateway, which connects the home network with the Internet.
The system was installed in twenty houses in the Tokyo area.
[8] proposed a home gateway based on the OSGI (Open
Service Gateway Initiative), which allows service providers to
access home automation systems for administration and
maintenance services. The proposed system is divided into
two subsystems. The first is the DSM (Digital Home Service
Distribution and Management System), which provides a user
interface for the control and monitoring of connected home
automation devices. The second is the Home Gateway, which
is responsible for managing the home automation system. This
open architecture raises privacy problems which, for some
users, may be much greater than the advantages offered by
granting third party access. [9] implements a home gateway
that accepts mobile phone signals and activates or deactivates
a LED representing a home device.
These systems have made a significant contribution to the
development of a home gateway. However, the existing
network infrastructure within the home environment has not
been taken into consideration when selecting the networks for
integration with the respective home gateways. Moreover, the
existing research has focused on the provision of remote
connectivity and has largely neglected investigating the
integration of existing local networks.
B. Analysis of the Existing Systems
The adoption of home automation technology by consumers
has been limited. We propose that, from the home automation
domain analysis, the problems limiting wide spread consumer
adoption can be grouped into five general categories. Firstly,
complex and expensive architecture: the existing systems
architectures generally incorporate a personal computer for
the purposes of network management and provision of remote
access. This adds additional complexity to the system, hence
increasing the overall fiscal expense. Secondly, intrusive
installation: the majority of systems require varying levels of
physical wiring in their architectures. This, in some cases, is
due to the expense of the alternative wireless technologies.
Hence, these systems require intrusive and expensive
installations. Thirdly, lack of network interoperability: both
home networks and the home automation systems which
utilise them have been developed and adopted in an unplanned
and ad-hoc manner. This has lead to a home environment
consisting of a complex maze of heterogeneous networks.
These networks and the systems that utilise them normally
offer little interoperability; leading to three potential problems
• duplication of monitoring activities, due to lack of
interoperability;
• the possibility of interference, between co-existing
networks; and
• the potential for two simultaneous, autonomous
actions on co-existing networks, interacting and
resulting in an undesirable outcome.
Fourthly, interface inflexibility: the existing systems offer
varying approaches for users to control and monitor the
connected devices. However, this is normally limited to a
single method of control, which offers users limited
flexibility. The systems which provide more than one interface
device normally provide different user interfaces and risk
confusing users. Finally, security and safety: the existing
approaches have not focused on security and safety problems
that may arise from their implementation. Moreover, the
systems that offer some degree of security have neglected the
problems with sharing information between devices produced
by multiple vendors for the purposes of establishing security.
C. Features of the proposed System
This paper presents a novel, stand alone, low-cost and
flexible ZigBee based home automation system. The
architecture is designed to reduce the system’s complexity and
lower fiscal costs. Hence, the system endeavours not to
incorporate complex and expensive components, such as a
high end personal computer, where possible. The system is
flexible and scalable, allowing additional home appliances
designed by multiple vendors, to be securely and safely added
to the home network with the minimum amount of effort. The
system allows home owners to monitor and control connected
devices in the home, through a variety of controls, including a
ZigBee based remote control, and any Wi-Fi enabled device
which supports Java. Additionally, users may remotely
monitor and control their home devices using any Internet
enabled device with Java support. A home gateway is
implemented to facilitate interoperability between
heterogeneous networks and provide a consistent interface,
regardless of the accessing device.
A virtual home pre-processes all communications before
they are realised on the real home automation system. All
communications are checked for security and safety before
being allowed to continue to their respective destinations.
This paper is organised as follows: Section 2 discusses the
developed home automation architecture, including a review
of the technology used. Section 3 describes the
implementation of the proposed system. Section 4 provides a
discussion of the system evaluation and Section 5 provides a
conclusion.
II. S
YSTEM ARCHITECTURE
This section describes the conceptual design of a flexible
and low cost home automation infrastructure (see Figure 1).
The home’s low data rate, control and monitoring needs are
catered for using Zigbee. The home’s high data rate needs,
such as multimedia applications, are met by the Wi-Fi (IEEE
802.11g) standard.
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IEEE Transactions on Consumer Electronics, Vol. 55, No. 2, MAY 2009
424
Fig. 1. Conceptual Architecture Overview.
A home gateway is implemented to provide interoperability
between the heterogeneous Zigbee and Wi-Fi networks, and
facilitate local and remote control and monitoring over the
home’s devices. A virtual home is implemented for the provision
of real time security and safety for the home and its inhabitants.
As depicted in Figure 1, the proposed system consists
primarily of four steps. Remote user can access the system
using the Internet. The remote user’s communications traverse
the internet until they reach the home network. They are then
wirelessly transmitted to the Home Gateway using the homes
Wi-Fi network. The Home Gateway is integrated with a
virtual home. These communications are checked and
processed by the home gateway and virtual home, as
discussed in greater detail later. This checking process
involves communication with the home networks coordinator,
which is integrated with the home’s device database and
contains the status of all connected devices. Once checked the
communications are sent to the real home automation system
and the respective device. Additionally, a local ZigBee based
remote control can be used to directly control connected
devices.
A. Residential Networks
As discussed, the proposed system architecture implements
a ZigBee based home automation network and a Wi-Fi based
multimedia network. Alternative standards could have been
integrated with the home gateway. However, the use of
Zigbee and Wi-Fi offers certain advantages. Zigbee
technology is designed to be used on applications that require
low data rate, low-cost, low power consumption, and two way
wireless communications. The Wi-Fi standard is designed to
provide relatively high data rate communications. Wi-Fi has
the advantage of an existing and wide spread presence in
homes in the United Kingdom. The combination of Zigbee
and Wi-Fi technologies has the potential to provide a
comprehensive home automation solution.
Zigbee technology
ZigBee is a radio frequency (RF) communications
standard based on IEEE 802.15.4. Figure 2 depicts the general
architecture of a Zigbee based home automation network. The
Zigbee coordinator is responsible for creating and maintaining
the network. Each electronic device (i.e. Washing Machine,
Television, Lamp etc) in the system is a Zigbee device
managed by the coordinator. All communication between
devices propagates through the coordinator to the destination
device. The wireless nature of ZigBee helps overcome the
intrusive installation problem with the existing home
automation systems identified earlier. The ZigBee standard
theoretically provides 250kbps data rate, and as 40kbps can
meet the requirements of most control systems, it is sufficient
for controlling most home automation devices. The low
installation and running cost offered by ZigBee helps tackle
the expensive and complex architecture problems with
existing home automation systems, as identified earlier.
Wi-Fi Technology
In the proposed system architecture, Wi-Fi is used for two
primary purposes. Firstly, it is the chosen communication
standard for multimedia applications in the home. Secondly, it
is used to provide access to the home automation system from
Wi-Fi enabled devices, as an alternative to the Zigbee based
local controller. This approach was taken because homes
increasingly have Wi-Fi networks and Wi-Fi enabled devices
such as PDA’s and mobile phones. The additional cost of a
Zigbee based controller in these situations is unwarranted.
Moreover, the high data rate nature of Wi-Fi allows for
greater flexibility in interface design. Wi-Fi implements the
IEEE 802.11 standard and offers wireless networking through
the use of radio frequency. There are different versions of this
protocol. The dominant protocol in use today is IEEE
802.11g, which operates in the unlicensed 2.4 GHz band and
provides a maximum raw data rate of 54 Mbps.
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K. Gill et al.: A ZigBee-Based Home Automation System
425
Fig. 2. Zigbee Home Automation Architecture.
The use of Wi-Fi offers several advantages over alternative
technologies. The Wi-Fi standard is more established in
homes in the UK than alternatives such as Bluetooth as a
wireless home networking technology. The result is less
equipment expense for the consumer, and the use of a
technology users are familiar with.
Network Coexistence
Heterogeneous and homogenous home networks may co-
exist with each other in the same environment. The problem of
interference between these networks increases as more and
more standards emerge which use the same communication
mediums. The interference problems between the possible
standards have been investigated. [10] researched the co-
existence of Zigbee, Bluetooth and Wi-Fi. The three protocols
use the same 2.4 GHz ISM band. It was found that Zigbee
interference has an insignificant effect on Wi-Fi throughput.
The effect of Wi-Fi on Zigbee throughput is a 10% reduction
in throughput, which provides an operational solution. The
experiment was repeated using Wi-Fi and Bluetooth. The
results showed a significant reduction in Wi-Fi throughput
and Bluetooth throughput. It can be concluded that the use of
the unlicensed part of the wireless spectrum by Zigbee causes
interference problems. Technologies such as Bluetooth,
microwave ovens and cordless telephones can cause
interference with Zigbee [11]. However, Zigbee and Wi-Fi
can exist together with less interference problems than
alternative technologies currently available, hence offering the
best combination available for use in our purposed
architecture.
B. Home Gateway
The home gateway, as depicted in Figure 1, is charged with
providing interoperability between different connecting
networks. The home gateway provides two primary functions
for the proposed architecture. Firstly, the home gateway
provides data translation services between the Internet, Wi-Fi,
and ZigBee networks. Secondly, the home gateway provides a
standardised user interface for devices connecting to the
ZigBee home network, remotely using the Internet or locally
using the Wi-Fi network. The home gateway does not provide
a standardised interface for the local ZigBee remote control
(See Figure 1). This decision was made to provide greater
freedom for interface design and avoid limitations that have to
be taken into consideration in the design of the low data rate,
low power ZigBee remote control interface. Although, as
depicted, the close cooperation between the home gateway
and device database allows for the real time control and
monitoring of all home devices, regardless of the access
device and network used. The home gateway is implemented
in the system architecture to overcome the problem of
insufficient network interoperability, identified in existing
home automation approaches. Moreover, the proposed
approach looks at the existing network structure within the
home environment and integrates networks which are
predominantly established in the existing home environment.
Additionally, the home gateway reduces the inflexibility in the
control modes of existing home automation systems; this is
undertaken through the prevision of manual, local and remote
control. Furthermore, the interface of the controlling devices
is standardised across the control modes.
C. Virtual Home
The virtual home, as depicted in Figure 1, is responsible for
the administration of security and safety for the home
automation system. The virtual home, as the name suggests, is
a virtual environment where the actions requested by users are
checked. For the purposes of security, all the messages
received by the virtual home are checked by authenticating the
senders, checking the integrity of the messages to ensure they
have not been tampered with, and protecting the
confidentiality of messages through the use of encryption. The
system’s safety is protected by ensuring the commands
received are appropriate for the respective home network and
that all changes requested fall within the specified safety
limits. The primary objective of the virtual home is to prevent
any event that may pose a security or safety concern from
implementation in the home networks. The virtual home is
included in the proposed architecture to tackle the security and
safety problems.
D. Device Engine
The home automation system is designed to be flexible,
allowing different devices designed by multiple vendors to be
connected. Each device incorporates a dedicated engine,
responsible for providing the necessary application
functionality and ZigBee network connectivity. Moreover,
each device engine may contain dedicated security and safety
measures. Critical devices should check all requested
operations to ensure that they will not result in an undesirable
outcome. Furthermore, collaboration with the virtual home
should provide the necessary information to facilitate secure
communications.
III. S
YSTEM IMPLEMENTATION
The implementation of the proposed system is illustrated in
Figure 3. As depicted, a ZigBee based home automation
system is implemented for the monitoring and control of
household devices. To cater for the household’s high data rate
needs, such as multimedia entertainment, a Wi-Fi network is
implemented. A home gateway has been developed to provide
interoperability between these networks. The home gateway
presents a unified interface for users to locally and remotely
access home networks. The security and safety of the home
automation network is realised through the development of the
earlier described virtual home on the Home Gateway. To
demonstrate the feasibility and effectiveness of the proposed
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