WIRELESS SENSOR NETWORKS: A SURVEY

Abstract

A wireless sensor network (WSN) (sometimes called a wireless sensor and actuator network (WSAN) are spatially distributed autonomous sensors to monitor physical or environmental conditions,[2] such as temperature,sound,pressure,etc. and to cooperati vely pass their data through the network to a main location. The more modern networks are bi-direction al,also enabling control of sensor activity. The development of wireless sensor networks was motivat ed by military applications such as battlefield surveillance;today such networks are used in many industrial and consumer applications,such as indus trial process monitoring and control,machine health moni toring,and so on. The WSN is built of "nodes" � fr om 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 typicall y several parts:a radio transceiver with an intern al antenna or connection to an external antenna,a mic rocontroller,an electronic circuit for interfacing with the sensors and an energy source,usually a battery or an embedded form of energy harvesting. A sensor nod e might vary in size from that of a shoebox down to t he size of a grain of dust,although functioning "m otes" of genuine microscopic dimensions have yet to be cr eated. The cost of sensor nodes is similarly variab le,ranging from a few to hundreds of dollars,dependin g on the complexity of the individual sensor nodes. Size and cost constraints on sensor nodes result in corr esponding constraints on resources such as energy,memory,computational speed and communications band width. The topology of the WSNs can vary from a simple star network to an advanced multi-hop wirele ss mesh network. The propagation technique between the hops of the network can be routing or flooding The relentless development of wireless technology p aves the way to novel applications,based on sensor netw orks or wireless systems. This paper aims at bringi ng together specialists of application areas along wit h researchers ...