Abstract
The device-free localization that locates an uncooperative target by analyzing its shadowing effect on wireless links in low-cost wireless sensor networks has become an attractive technique. Due to its ability of realizing localization without the need of equipping the target with any wireless device, device-free localization has lots of potential applications ranging from emergency rescue to patient monitoring. However, since the change of the received signal strength on links easily becomes unpredictable due to all kinds of dynamical factors, device-free localization is still a challenging problem. In this article, we propose a novel two-step sequential device-free localization method to enhance device-free localization performance. The sequential device-free localization first utilizes the geometric-based method to quickly obtain the coarse positioning result with low storage and computational requirements, and then exploits the location information of selected wireless nodes to improve the accuracy of the geometric-based localization result based on the optimization-based method, which ensures its robust performance. Experimental results in indoor and outdoor scenarios demonstrate the effectiveness and robustness of the proposed scheme.
Highlights
Target localization and tracking techniques in wireless sensor networks have received lots of attentions during the past two decades since the position information is extremely valuable for commercial and military applications
To demonstrate the applicability of the sequential DFL method (SDFL) method, we develop a prototype device-free localization (DFL) system which is made up of 24 wireless nodes in an open outdoor environment (Scene 1) or 16 wireless nodes in a rich multipath indoor scenario (Scene 2) to carry out extensive experiments
It is not necessary to place the nodes in a uniform spacing, in this article, all wireless nodes are evenly spaced at the perimeter of the deployment region for simplicity
Summary
Target localization and tracking techniques in wireless sensor networks have received lots of attentions during the past two decades since the position information is extremely valuable for commercial and military applications. Unlike cooperative localization techniques that equip the target with a wireless device such as a radio frequency identification (RFID) tag, device-free localization (DFL) is a new concept that allows the localization and tracking for targets which neither carry any devices nor participate actively in the localization process.[1,2] DFL technologies are useful in a wide number of applications including intrusion detection, border protection, emergency rescue, patient or elder monitoring, and so on, where targets being tracked cannot be expected to cooperate with the localization system.
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