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ZigBee Sensor Network for Advanced Metering Infrastructure
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I. INTRODUCTION
he struggle between global warming and human beings is
well recognized by the international society. Scientists
devoted their effort into the development of renewable
energies while governors/administrators audit and control
energy consumption based on regulation. In view of the
compulsory energy consumption control in near future,
researchers have developed energy aware technology such as
ZigBee [1], [2]. ZigBee is a wireless sensor network for home
and building automation. Recently, ZigBee has been widely
adopted for both metering as well as energy management.
There is no doubt that Advance Metering Infrastructure
(AMI) plays an important role in the metering system.
However, the research of AMI is at its infancy. The two key
features: “easy to deploy” and “robust communication” are the
two most important requirements of AMI. ZigBee is
considered as one of the most potential candidates since the
platform is a kind of wireless senor networking technology
with strong mesh capability. In this paper, a ZigBee AMI
(ZAMI) system is proposed to cater for the demand side
management. Bridging the gap between users and utilities in
order to minimize the green gas emission is the ultimate goal
of ZAMI.
II. SYSTEM OVERVIEW AND ARCHITECTURE
This section introduces the ZAMI and explains the
operations. The ZAMI (Fig. 1) is an end to end ZigBee
The support from Citycom Technology Ltd. is gratefully acknowledged.
H. Y. Tung is with the Department of Electronic Engineering, City
University of Hong Kong (email: hytung[at]student.cityu.edu.hk).
K. F. Tsang is the Managing Director of Citycom Technology Ltd. Hong
Kong and also an Associate Professor of the Department of Electronic
Engineering, City University of Hong Kong (email: ee330015[at]cityu.edu.hk).
K. L. Lam is with the Department of Electronic Engineering, City
University of Hong Kong (email: kalunlam[at]student.cityu.edu.hk).
metering solution which includes three basic elements: the in
home display, the smart meter and the utility server. The smart
meter measures the energy consumption of an individual user
and sends meter readings to the utility server periodically. The
utility server stores the meter reading for profiling record and
analysis as well as billing purpose. Under critical situations,
the utility system takes over the control of users’ high energy
demand appliances such as air conditioner via In-home
display. As a result, the peak demand of electricity is reduced.
The In-home display not only provides the timely consumption
and pricing information by interacting with the ZigBee Main
Circuit Box (ZMCB) but also teams up with other ZigBee
devices such as light switches, power outlets, computers and
appliances to form a HAN and thus facilitating the aim of
home automation and energy management. To audit the energy
usage, a ZigBee Micro Smart Meter is embedded inside the
ZMCB to capture the energy consumption of major appliances.
As a result, the energy profiles are captured. In addition, the
aging report and analysis of electrical appliances can be
conducted by the ZigBee In-home display. Key applications
include alerting the owners of high surges which may thus
cause fire. Other potential applications include the shut down
of some appliances in the case of shortage of electricity
experienced by the utility, and in such a circumstance,
consumers may enjoy a lower energy rate. To facilitate system
reliability and efficiency, multiple channels and channel
hopping are developed to handle fast and bursty data. The
network architecture of ZAMI, incorporating multiple channel
capability, for high rises, is illustrated in Fig. 1.
Fig. 1 Network Architecture of ZAMI
The network of ZAMI is divided into two parts: the
backbone for ordinary AMI and mesh networks for HAN
services. In-home displays and smart meters are located at
different premises of each floor. If the In-home displays/smart
ZigBee Sensor Network for Advanced Metering
Infrastructure
Hoi Yan Tung, Kim Fung Tsang, Member, IEEE, and Ka Lun Lam
T
978-1-4244-4316-1/10/$25.00 ©2010 IEEE
Authorized licensed use limited to: Guru Anandan Saminathan. Downloaded on May 10,2010 at 05:49:12 UTC from IEEE Xplore. Restrictions apply.
meters are situated at locations that cannot be reached by the
network, then a ZigBee router is added to relay the message to
isolated devices. Based on the In-home display, ZMCB,
ZigBee light switches, ZigBee power outlets and other ZigBee
devices, a ZigBee mesh network can be easily formed in each
household/premises on a floor. The timely energy consumption
and pricing information can be provided to users at any time.
Vertically, the meter reading can be collected from the ZigBee
mesh network. The collected data is sent the control centre by
multiple hopping. The control centre then forwards the data to
utility system via internet/ GPRS. The most challenging
mission of ZAMI is that the backbone network must ensure the
data flowing through different floor smoothly with acceptable
signal strength and yet reasonable low latency. Based on the
demand, multi-channeling and channel hopping are developed.
To facilitate fast data delivery (and thus low latency), multiple
channels operate on the ZAMI backbone network to share the
traffic loadings. Hence the transmission time decreases
dramatically as the number of collateral channel increases.
Other natural enemy of wireless technology is the potential
interference from friendly users of WiFi and Bluetooth [3]. To
combat potential interference, ZAMI has already incorporated
a frequency hopping scheme for interference avoidance.
Consider the case that a ZigBee router on the 6th floor sends
the collected meter data to the control center on two channels:
channel 1 and channel 2. Suppose channel 1 suffers from the
interference on the 3rd floor. Once the sender detects the
transmission fails, the backbone routers initiates a channel hop
by replacing the channel 1 with channel 3, thus avoiding
interference. The data are then sent to the concentrator from
which the data will be sent to the backend server.
To provide confidentiality, in the data delivery, end to end
AES128 bits encryption are provided. Moreover, load
balancing and redundant server are devised to facilitate high
availability. A report can be provided for meter data profiling
and billing. The case study of the ZAMI is presented in the
following section.
III. CASE STUDY AND PERFORMANCE EVALUATION
A case study is examined to evaluate the performance of the
ZAMI system. In the study, there are thirty-floors in the
highrise and eight apartments on each floor. In this
investigation, the control center collects the meters data once
per day and the smart meter stores latest 10 records. To gain
more insight, the system performance with varying
transmission powers is evaluated
Fig. 2 investigates the relationship between the throughput
improvement of dual channel operation and the transmission
power. It is seen that the throughput increases as the
transmission power increases since the frequency of
retransmission is reduced. As the number of retransmission
trends to zero, the maximum throughput is achieved. Since
high transmission power causes the side effect of strong
interference to other operating channel, namely Neighbor
channel interference (NCI), the throughput improvement
decreases as the transmission power increases. In such
circumstance, the channel experiences stronger inference from
other operation channel. Furthermore, Fig. 2 studies the
relationship between the delay improvement of dual channel
operation and the transmission power. It is seen that the two
operation channel shares the traffic workload and thus the
delay is improved by 30% to 50%. Fig. 5 reveals that the delay
improvement drops while the transmission power increases.
The reason is attributed to the fact that the operation channel
experiences stronger NCI.
Fig. 2 The Throughput Improvement (%) of dual channel
operation
IV. CONCLUSION
Automatic Meter Infrastructure enables interactive
communication between users and utilities and is the most
active area in the development of metering. In this paper, a
ZigBee Advance Metering infrastructure (ZAMI) is proposed
and implemented. The system dedicates to automatic meter
data collection and energy auditing and management. The
ZAMI, comprises of the ZigBee Energy Manager, ZigBee light
switches, ZigBee power outlets, ZigBee-Infrared converters,
ZigBee In-home displays, facilitates energy auditing, energy
management and appliance aging analysis. An alert signal and
aging report can be sent to users in case critical aging and high
surges occur. To provide confidentiality, in the data delivery,
end to end AES128 bits encryption are provided. Moreover,
load balancing and redundant server are devised to facilitate
high availability. To ensure the system efficiency and
reliability, a multichannel frequency hopping system is
developed which coexists with potential interferers such as
WiFi or Bluetooth. A system model of ZAMI is developed to
evaluate the performance of multi channel of ZAMI. The
system performance including the throughput and the
transmission time are also analyzed. It is investigated that high
transmission power causes neighbor channel interference, and
that the throughput improvement decreases as the transmission
power increases. By incorporating dual channels, the delay is
improved by 30% to 50%.
V. REFERENCE
[1] IEEE Std 802.15.14: Wireless Medium Access Control (MAC) and
Physical Layer (PHY) Specifications for Low-Rate Wireless Personal
Area Networks (LR-WPANs), 2003.
[2] K. F. Tsang, H. Y. Tung, K. L. Lam, “ZigBee: From Basics to Designs
and Applications”, Prentice Hall, 2009.
[3] K. F. Tsang, “Wireless Communication”, Prentice Hall, 2008.