Wireless sensor network ||This article needs additional
citations for verification. (May 2011)| A wireless sensor
network (WSN) consists of spatially distributed autonomous
sensors to monitor physical or environmental conditions, such as
temperature, sound, pressure, etc. and to cooperatively pass
their data through the network to a main location. The more
modern networks are bi-directional, also enabling control of
sensor activity. 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 industrial process monitoring
and control, machine health monitoring, and so on. The WSN is
built of "nodes" – from a few to several hundreds or even
thousands, where each node is connected to one (or sometimes
several) sensors. Each such sensor network node has typically
several parts: a radio transceiver with an internal antenna or
connection to an external antenna, a microcontrolle