2 Advances in Wireless Sensor Networks

INTRODUCTION The origins of networks of sensors can be traced back to the 1980s when DARPA initiated the Distributed Sensor Networks program. However, recent advances in microprocessor fabrication have led to a dramatic reduction in both the physical size and power consumption of such devices. Battery and sensing technology as well as communications hardware have also followed a similar miniaturization trend. The aggregation of these advances has led to the development of networked, millimeter-scale, sensing devices capable of complex processing tasks. Collectively these form a Wireless Sensor Network (WSN), thus heralding a new era of ubiquitous sensing technology and applications. Large-scale deployments of these networks have been used in many diverse fields such as wildlife habitat monitoring (Mainwaring, 2003,) traffic A number of commercial WSN platforms have been launched in recent years. Examples constituent components of a WSN continues unabated, power consumption likewise diminishes, thus the current generation of sensors can function perfectly for years using standard AA 3 batteries (Polastre, 2004). Alternative solutions may not require any batteries; for example iBeans (Rhee, 2003) coupled with energy harvester can operate by scavenging energy from tiny vibrations that occur naturally. Miniaturized solar panels are another possible solution for outdoor operation. Production costs of single nodes are estimated to be less than a dollar, a significant cost reduction over the price of older sensor models, thus paving the way for large-scale WSN deployments, possibly consisting of a number of nodes several orders of magnitude greater than that in ad-hoc networks (Akyildiz, 2002).