A wireless sensor network (WSN) is a wireless network consisting of autonomously spatially distributed devices that use sensors to monitor physical or environmental conditions. A WSN system incorporates a gateway that provides wireless connectivity back to the wired world and distributed nodes. The wireless protocol you select depends on your application requirements. Some of the available standards include 2.4 GHz radios based on standards IEEE 802.15.4 or IEEE 802.11 (Wi-Fi) or proprietary radios, which are usually 900 MHz.
Wireless sensor networks (WSNs), sometimes called sensor networks and wireless actuators (WSANs), are spatially distributed autonomous sensors for monitoring physical or environmental conditions, such as temperature, sound, pressure, etc. One main location. The most modern networks are bidirectional, also allowing the control of the activity of the sensor. The development of wireless sensor networks was motivated by military applications such as battlefield surveillance; Today such networks are used in many industrial and consumer applications, such as monitoring and control of industrial processes, monitoring the health of machines.
The WSN is constructed of "nodes" - from a few to several hundred or even thousands, where each node is connected to one (or sometimes several) sensors. Each of such sensor network nodes typically has several parts: a radio transceiver with an internal antenna or a connection to an external antenna, a microcontroller, an electronic circuit for interfacing with the sensors and a power source, usually a Battery or an embedded form of energy collection. A sensor node can range in size from that of a shoebox to the size of a grain of dust, although functional "motes" of genuine microscopic dimensions have not yet been created. The cost of sensor nodes is similarly variable, ranging from a few to hundreds of dollars, depending on the complexity of the individual sensor nodes. The size and cost constraints of sensor nodes result in constraints corresponding to resources such as power, memory, computational speed, and communications bandwidth. The WSN topology can range from a single star network to an advanced multi-hop wireless mesh network.