Wireless Sensor Networks - An Emerging Technology
By Udit Agarwal
Wireless sensor networks (WSNs) are an emerging technology consisting of small, low-power devices that integrate limited computation, sensing and radio communication capabilities. The technology has the potential to provide flexible infrastructures for numerous applications, including healthcare, industry automation, surveillance and defense. Wireless sensor networks promise an unprecedented fine-grained interface between the virtual and physical worlds. They are one of the most rapidly developing new information technologies, with applications in a wide range of fields including industrial process control, security and surveillance, environmental sensing, and structural health monitoring.
A wireless sensor network is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations. The development of wireless sensor networks was originally motivated by military applications such as battlefield surveillance. However, wireless sensor networks are now used in many civilian application areas, including environment and habitat monitoring, healthcare applications, home automation, and traffic control.
In addition to one or more sensors, each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small micro controller, and an energy source, usually a battery. The envisaged size of a single sensor node can vary from shoebox-sized nodes down to devices the size of grain of dust, although functioning 'motes' of genuine microscopic dimensions have yet to be created. The cost of sensor nodes is similarly variable, ranging from hundreds of dollars to a few cents, depending on the size of the sensor network and the complexity required of individual sensor nodes. Size and cost constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth. A sensor network normally constitutes a wireless ad-hoc network, meaning that each sensor supports a multi-hop routing algorithm (several nodes may forward data packets to the base station). In computer science and telecommunications, wireless sensor networks are an active research area with numerous workshops and conferences arranged each year.
The applications for WSNs are many and varied. They are used in commercial and industrial applications to monitor data that would be difficult or expensive to monitor using wired sensors. They could be deployed in wilderness areas, where they would remain for many years (monitoring some environmental variables) without the need to recharge/replace their power supplies. They could form a perimeter about a property and monitor the progression of intruders (passing information from one node to the next). There are many uses for WSNs. Typical applications of WSNs include monitoring, tracking, and controlling. Some of the specific applications are habitat monitoring, object tracking, nuclear reactor controlling, fire detection, traffic monitoring, etc. In a typical application, a WSN is scattered in a region where it is meant to collect data through its sensor nodes. Another class of application is the so-called smart space.
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Wireless Sensor NetworkBased Tunnel Monitoring
ABSTRACT
In this paper we describe the development and deployment of a
wireless sensor network (WSN) to monitor a train tunnel during adjacent
construction activity. The tunnel in question is a part of the
London Underground system. Construction of tunnels beneath the
existing tunnel is expected to cause deformations. The expected deformation
values were determined by a detailed geotechnical analysis.
A real-time monitoring system, comprising of 18 sensing units
and a base-station, was installed along the critical zone of the tunnel
to measure the deformations. The sensing units report their data
to the base-station at periodic intervals. The system was used for
making continuous measurements for a period of 72 days. This
window of time covered the period during which the tunnel boring
machine (TBM) was active near the critical zone. The deployed
WSN provided accurate data for measuring the displacements and
this is corroborated from the tunnel contractor’s data.
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