Wireless sensor network (WSN) refers to a group of spatially dispersed and dedicated sensors for monitoring and recording the physical conditions of the environment and organizing the collected data at a central location. WSNs measure environmental conditions like temperature, sound, pollution levels, humidity, wind, and so on.
The sensor networks are made up of devices that communicate with the wireless radio and cooperatively detect physical or environmental conditions. They offer great visibility on physical environmental processes. Wireless sensor networks (widely called WSN) have been used in a pervasive field of applications such as scientific exploration, infrastructure protection, military, social and assisted living, and many others. Sensor networks are also particularly useful in catastrophic or emergency scenarios, such as floods, fires, volcanoes, battlefields, where human association is very dangerous and infrared networks are very expensive.
The WSN is made up of "nodes" - from a few to several hundred or even several, where each node is connected to one (or sometimes several) sensors. Each of these sensor network nodes has several parts: a radio transceiver with an internal antenna or a connection to an external antenna, a microcontroller, an electronic interface circuit with a battery or an integrated form of recovery. A sensor node can vary in size from that of a shoe box to the size of a speck of dust, while functional "motes" of true microscopic dimensions have yet to be created. The cost sensor nodes are also variable, ranging from a few to a few hundred dollars, depending on the complexity of the individual sensor nodes. Size and cost constraints on the sensor nodes cause the constraints on resources such as energy, memory, computing speed, and communications bandwidth. WSN topology can vary from a simple star network to an advanced multi-hop wireless mesh network. The propagation technique between network hops can be routed or flooded to a single star network to an advanced multi-hop wireless mesh network