感測器(sensor)定位(localization)是無線感測網路(Wireless Sensor Networks)的一種應用，感測器的位置資訊對於在涵蓋範圍、偵查、繞送、追蹤和救援等問題上，都需要依據可靠的定位資訊來協助，所以定位就變得相當的重要，而實際能運用在軍事安全、工業控制、環境生態以及家中監控。簡而言之，當硬體設施與通訊協定建立完成後，依所需要的目的做特定的感測，再透過演算法定位，就能達成各類的應用。

在本篇論文中我們提出分散式無線感測器的定位演算法，透過具有裝備全球定位系統(Global Positioning System)的移動信標(mobile beacon)來幫助感測器定位，並利用RSSI(Received Signal Strength Indicator)的特性，透過我們的演算法可將距離量測誤差降低到最小。模擬結果表示論文方法有效提升感測器定位效率與精準度。

Wireless sensor networks (WSNs) have wide application in fields such as military monitoring, environmental observation, disaster relief, and emergency medical service. Wireless sensor networks are composed of several sensor nodes that communicate via wireless technology. Each node can sense surrounding environment and perform limited computations. Localization is one of the most important topics in WSN research. An accurate localization scheme can support transmission of the sensor position information, routing and technology services. So far, some localization methods have been presented that could be implemented using one or more beacon nodes with Global Positioning System (GPS). GPS coordinates are a good estimate of sensor position, but it is too expensive to equip each sensor with GPS. A feasible solution is to designate a small number of sensor nodes as anchor points or beacons and equip them with GPS. They can help other sensor nodes locate themselves using the information broadcast by the beacons.

Locating the sensor nodes is a fundamental problem in developing applications for wireless sensor networks. In this thesis, we present a distributed localization algorithm for wireless sensor networks. The node locations are computed by performing elementary operations based on the RSSI value and the position of the mobile beacon. Simulation results show that the proposed scheme is very efficient and that the node positions can be determined accurately.

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