Industrialised, Integrated, Intelligent sustainable Construction - I3con

SUSTAINABLE CONSTRUCTION HANDBOOK 2
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• WSN tasking to enable configuring sensor nodes for data collection by means of the tasking
middleware.
The WSN architecture assumes the role of service provider as far as data collection and information
management is concerned. This justifies the need for a WSN service interface to be defined and
exposed to the SOA infrastructure, in order to hide the complexity and heterogeneity of the
underlying WSNs.
The WSN architecture is implemented over two sensor platforms, i.e. the sensor node and the
gateway, while at a higher layer of abstraction a Server entity (i.e. Virtual Gateway) is responsible for
managing the WSN nodes. A gateway essentially is a network-bridging device, which connects each
WSN zone to the Intranet/enterprise network. The Virtual Gateway is made aware of various WSN
zones available in the enterprise building and their respective zone gateways by accessing a topology
map. When applications/services require interaction with the WSN architecture as a whole, this occurs
through the relevant WSN service interface that interacts with the Virtual Gateway. The Virtual
Gateway is equipped with an enterprise middleware layer, which is responsible for communicating
with the WSN service interface of the SOA. We used a web services model that constitutes a means
for various software platforms to interoperate, without any prerequisite regarding platform and
framework homogeneity being necessary. A WSN environment is essentially a collection of resources
(i.e. sensors) that continuously monitor their environment (i.e. get measurements). We have therefore
defined a REST-based (REpresentational State Transfer) style SOA to enable integration of the WSN
with enterprise services [5], [6], [7].
By exploiting the aforementioned architecture, an external application has been developed to monitor
the operational health of WSN, identify possible operational problems in the network, and display
these to administrators via a web-based user interface. The application also enables the structure of
the WSN to be browsed through the user interface. The application is regarded as a consumer of WSN
data and a service provider to the external clients (managers or occupants) in the SOA paradigm. The
application assumes that the WSN is comprised of one or more wired gateways, with each gateway
servicing a number of wireless motes in a zone. A mote may contain several sensors, each sampling a
different quantity, e.g. light, temperature, humidity, presence, CO2, etc. Associated with each sensor is
a collection of measurements, each with a time-stamp and a value.
The remainder of this paper is structured as follows. Section 2 briefly describes the WSN generic
security issues and implementation of an access control service. Section 3 provides a brief overview
of related work and then describes the design and configuration of WSN health monitoring
application. Section 4 provides the instructions for the operation of the application. Section 5
discusses the interface of the application to the virtual gateway for accessing to the required data. A
brief summary is given in Section 6.
WSN Security and Access Control Service
Before explaining the WSN health monitoring application that we have developed, here, we briefly
discuss the WSN security as an important and related aspect to the health of WSN. Given the
vulnerabilities of WSNs, security is a highly desirable and necessary function, depending on the
context and the physical environment in which a sensor network may operate [13].
Since WSNs use wireless communications, they are vulnerable to attacks, which are rather simpler to
launch when compared to the wired environment [14]. Many wired networks benefit from their
inherent physical security properties. However, wireless communications are difficult to protect; they
are by nature a broadcast medium, in which adversaries can easily eavesdrop on, intercept, inject, and
alter transmitted data. In addition, adversaries are not restricted to using sensor network hardware.
They can interact with the network from a distance by using radio transceivers and powerful
workstations. Sensor networks are vulnerable to resource consumption attacks. Adversaries can
repeatedly send packets to waste the network bandwidth and drain the nodes’ batteries. Since sensor
networks are often physically deployed in less secure environments, an adversary can steal nodes,