Observing various aspects of the environment is repeatedly done everyday. For instance humans are capable of sensing temperature, which may stimulate certain actions to accommodate their preferences such as switching on/off the air conditioning system. In a large number of industrial plants, monitoring of equipment is done by humans and their judgement determines when a component is to be replaced. Sensors are used to substitute humans for monitoring events and for sensing physical properties of an environment. Clearly one sensor on its own can not give precise information about the overall attributes of an environment or the state of an industrial equipment. Hence by increasing the number and the types of sensors used, not only is the coverage increased but also the gathered data more closely resembles properties of the actual physical environment. Using a large number of sensor has a number of valuable advantages;

Management of large number of sensors on per sensor basis is not practical, which is why using a networked set of sensors is appealing. However networked sensors have some constraints. The major shortcomings of networked sensor networks are:

Advances in technology has allowed for development of very small devices capable of processing, wireless communication and also sensing phenomena(physical attributes and properties being sensed are commonly referred to as phenomena in context of sensor networks). In comparison to networked sensors, the two most notable points about these devices are that i) they are very power efficient, which means they can run on batteries for a long time and ii) they can communicate wirelessly, which means there is no longer a need for cumbersome and expensive cabling. The setup of such networks have become popular in various observation applications(e.g. habitat monitoring) and spawn the field of wireless sensor network(WSN).

Jenson Taylor 2008-01-25