I. Introduction
Wireless sensor networks (WSNs) can be defined as a self-configured and less-infrastructure wireless networks to help people to monitor or surveillance physical condition changes, such as sound, temperature, voice stream, pressure, motion, etc. [1]–[4]. The main purpose is to sense and transfer the data via the network to the base station which is able to process the data and interface with users. Originally, WSNs are motivated by military applications, such as large scale ocean surveillance and ground target tracking systems. Then this promising technique has been extended to varieties of areas, such as environmental monitoring, health care applications and industrial process control [5] [6]. It is obvious that all these purposes emphasize the importance of position information, which is critically useful for coverage, deployment, routing, target tracking and rescue, thus highlighting the accuracy of these position information. Generally, the major ways to collect position information of nodes in prior are able to be classified as follows,
recording the location reference of each node during the deployment phase manually;
equipping the Global Positioning System (GPS) module onto each node, which is extremely costly and energy consuming [7];
placing GPS module onto some special nodes as anchors, and others are able to estimate their own positions with the help of anchors, which is called localization method [1].