| Wireless sensor networks (WSNs) are an emerging | | | | created. The cost of sensor nodes is similarly variable, |
| technology consisting of small, low-power devices | | | | ranging from hundreds of dollars to a few cents, |
| that integrate limited computation, sensing and radio | | | | depending on the size of the sensor network and the |
| communication capabilities. The technology has the | | | | complexity required of individual sensor nodes. Size |
| potential to provide flexible infrastructures for | | | | and cost constraints on sensor nodes result in |
| numerous applications, including healthcare, industry | | | | corresponding constraints on resources such as |
| automation, surveillance and defense. Wireless sensor | | | | energy, memory, computational speed and |
| networks promise an unprecedented fine-grained | | | | bandwidth. A sensor network normally constitutes a |
| interface between the virtual and physical worlds. | | | | wireless ad-hoc network, meaning that each sensor |
| They are one of the most rapidly developing new | | | | supports a multi-hop routing algorithm (several nodes |
| information technologies, with applications in a wide | | | | may forward data packets to the base station). In |
| range of fields including industrial process control, | | | | computer science and telecommunications, wireless |
| security and surveillance, environmental sensing, and | | | | sensor networks are an active research area with |
| structural health monitoring. | | | | numerous workshops and conferences arranged each |
| A wireless sensor network is a wireless network | | | | year. |
| consisting of spatially distributed autonomous devices | | | | The applications for WSNs are many and varied. |
| using sensors to cooperatively monitor physical or | | | | They are used in commercial and industrial applications |
| environmental conditions, such as temperature, | | | | to monitor data that would be difficult or expensive |
| sound, vibration, pressure, motion or pollutants, at | | | | to monitor using wired sensors. They could be |
| different locations. The development of wireless | | | | deployed in wilderness areas, where they would |
| sensor networks was originally motivated by military | | | | remain for many years (monitoring some |
| applications such as battlefield surveillance. However, | | | | environmental variables) without the need to |
| wireless sensor networks are now used in many | | | | recharge/replace their power supplies. They could |
| civilian application areas, including environment and | | | | form a perimeter about a property and monitor the |
| habitat monitoring, healthcare applications, home | | | | progression of intruders (passing information from |
| automation, and traffic control. | | | | one node to the next). There are many uses for |
| In addition to one or more sensors, each node in a | | | | WSNs. Typical applications of WSNs include |
| sensor network is typically equipped with a radio | | | | monitoring, tracking, and controlling. Some of the |
| transceiver or other wireless communications device, | | | | specific applications are habitat monitoring, object |
| a small micro controller, and an energy source, usually | | | | tracking, nuclear reactor controlling, fire detection, |
| a battery. The envisaged size of a single sensor node | | | | traffic monitoring, etc. In a typical application, a WSN |
| can vary from shoebox-sized nodes down to devices | | | | is scattered in a region where it is meant to collect |
| the size of grain of dust, although functioning 'motes' | | | | data through its sensor nodes. Another class of |
| of genuine microscopic dimensions have yet to be | | | | application is the so-called smart space. |