WIRELESS SENSORS

WIRELESS SENSORS
A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions , such as temperature , sound, vibration , pressure , motion or pollutants , at different locations . The development of wireless sensor networks was originally motivated by military applications such as attlefield surveillance . However , wireless sensor networks are now used in many civilian application areas , including environment and habitat monitoring, healthcare applications, home automation, and traffic control.
In addition to one or more sensors , each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small microcontrolle r, and an energy source, usually a battery. The envisaged size of a single sensor node can vary from shoebox-sized nodes down to devices the size of grain of dust , although functioning 'motes' of genuine microscopic dimensions have yet to be created.The cost of sensor nodes is similarly variable, ranging from hundreds of dollars to a few cents , depending on the size of the sensor network and the complexity required of individual sensor nodes. Size and cost constraints on sensor node result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth.A sensor network normally constitutes a wireless a d - hoc network , meaning that each sensor supports a multi – hop routing algorithm ( several nodes may forward data packets to the base station).