Wireless sensor networks
Perceive the world like never before
Recent advances in microelectronics and wireless communications have technically enabled to build wireless sensor networks (WSN) on a larger scale. There are plenty of potential applications. However, a number of challenges are preventing an immediate and wide deployment of applications based on this technology.
Every year, many people die in avalanches, because it takes too long to find them. Severe forest fires destroy forests and threaten habitat areas as seen in Portugal recently. Floods have become a frequently occurring catastrophe in central Europe in the past few years. The ability to instantly detect such disasters would help to take immediate action for reducing the damage and for saving lives. These are just a few examples of applications that Wireless Sensor Networks could be deployed for in the future.
A typical sensor network consists of a large number of sensor nodes which are densely deployed in the region of interest and which communicate in order to accomplish a given task. Sensor nodes are the key elements of a WSN. Progress in developing Microelectromechanical Systems (MEMS) has enabled new classes of sensors, e.g. for measuring gravitational forces or acceleration. There are also visual, acoustic, thermal, and magnetic types of sensors and combinations of it; others can detect fog, pressure, chemical concentrations, or seismic activities. However, there is more to a sensor node than only the sensing capability. A sensor node also contains a microprocessor, data storage, a data transceiver, and – maybe the biggest issue currently – an energy source. Besides the sensor node, networking constitutes another key aspect of WSN. The following article in this cover theme gives a good overview on the various aspects and challenges that still have to be solved in WSN networking and the related security issues.
Resource constraints everywhere
If we look into the design of WSN, it quickly becomes obvious that the limited availability of resources is a key criterion which has to be considered for designing WSN. Sensor nodes must – for a dense deployment – be small in size, low cost, and yet multifunctional. They must operate for long periods of time under possibly harsh environmental conditions.
Energy is a scarce resource in a sensor node. Using small batteries is one way to provide power, although not a very environment–friendly one, as deployed sensors can often not be re-collected after the end of their operation. Harvesting energy e.g. solar radio waves, or vibrations are alternative ways, though they seem still to be in an early stage. These constraints result in a limited processing speed, storage capacity, and communication frequency and bandwidth in WSN. Communication is the most energy consuming operation. That is why WSN process data within the network wherever possible. Mastering these challenges is a prerequisite before mass deployment can be started.
Ample application areas
WSN enable that we can perceive what takes place in the outside world, in our environment, in a level of detail that was not possible before. The main capability that WSNs are offering is monitoring. The wide, dense, and relatively easy deployment of sensor nodes, for example by dropping from a plane or ship, or delivery by an artillery missile, makes it possible to deploy a WSN instantly on demand, to reach dangerous or other types of hardly or even inaccessible areas (natural reserves, underwater, mountain areas, battlefields etc.), and to acquire information from the region of interest in a fine granularity. Some of the main application areas are:
I recently got aware of another application which has been described in a scientific paper: In a scenario called “Biosensor Network”, animals (here: rats) are backpacked with a tiny sensor node. Based on recent research results, showing that animals can be guided remotely by stimulating regions of their brain, an animal WSN can be formed which could be applied e.g. for search and rescue operations.
Though this scenario caused some ethic concern with me and also sounds slightly like fantasy, it gives a glimpse of the potential of this technology. I hope the readers of Eurescom mess@ge will find the articles of the cover theme in this issue informative, inspiring, and enjoyable.
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