I. Introduction II
Wireless Sensor Networks (WSNs) are composed of a large number of sensor nodes that consists of four components: sensing element, processing element, transmission element and power element. The potential applications of Wireless Sensor Networks are environmental monitoring, target tracking, surveillance, military, security, etc. In Wireless Sensor Networks, the fundamental problem is localization i.e, determining the location of nodes. Global Positioning System (GPS) is the most obvious solution of this problem. But the huge, expensive cost and power consumption of GPS, different algorithms are developed for the localization. While designing the localization algorithms the key aspects or issues such as: limited resource, the number and density of node network topology, device capability, localization accuracy, kind of signals and mobility of node (static node or mobile node) must be considered [1].