Wireless sensor network (WSN) localization has received a great deal of attention in recent years. Using the information of received signal strength (RSS) measurements, many decentralized localization methods have been proposed to decrease the sensor node’s energy consumption. Generally, the large-scale behavior of the signal received at each sensor node can be modeled as the distance-dependent path loss model in indoor environment, thus the performance of RSS-based localization methods will be affected by the estimation accuracy of path loss exponent (PLE).
In this thesis, we propose a joint positioning and PLE estimation method based on recursive weighted least squares (RWLS) optimization for WSNs. We first formulate two recursive-in-time cost functions from a sum of the local cost functions and then prove that the minimization of the recursive-in-time cost functions can be realized by the joint positioning and PLE estimation method. In other words, our method is derived from the minimization of the recursive-in-time cost function and then realized in an iterative, decentralized manner. In the proposed method, the PLE and the target location are computed iteratively by taking a weighted average of the local estimates according to the reliability of the sensor nodes, and the reliability is concerning about the PLE and distance estimates. During each iteration, a sensor node computes a new PLE estimate and a new location estimate by its own observation and the most update passed over by the sensor node responsible for the pervious iteration. The newest estimates are circulated and updated among the sensor nodes in the localization procedure. Computer simulation results demonstrate that our method has better location accuracy than the recursive weighted least squares (RWLS) method.

無線網路中的定位在最近這些年受到很大的關注。利用測量訊號強度大小(RSS)的資訊，許多為了要減少感測節點能量消耗的分散式定位演算法相繼被提出。一般來說，在室內的環境中，距離與收到訊號的關係可以利用距離相關的通道衰減模型來表示，因此，這模型的好壞與否受到通道衰減指估測的精準度的影響。
在本篇論文中，基於遞迴式加權最小平方法，我們對於無線感測網路提出了一種結合定位與訊號衰減指數估測的演算法。首先，我們累加了區域的成本函數形成兩個具有及時遞迴性質的成本函數，然後證明最小化這個及時遞迴的成本函數可以被聯合定位與通道衰減指數估測的方法實現。也就是說，我們的方法是最小化這兩個及時遞迴的成本函數所得到，然後利用迴圈與分散式的方式實現。在這個方法中，目標物的位置與訊號衰減指數是根據感測結點的可靠度迴圈式地計算加權平均每個節點自己的估計值所得到，而這個可靠度與通道衰減指數和距離的估測有關。在每一個迴圈中，一個參與定位的節點藉由自己的觀察值和負責前一個迴圈的節點所傳過來最後更新的估測值計算最新的訊號衰減指數的估測值與目標物的估計位置。在整個過程中，最新的估測值不斷地被參與的節點環繞且更新。電腦的模擬結果顯示，我們所提出結合定位與訊號衰減指數估測的方法在估測位置的精準度方面是表現得比之前RWLS的方法好。

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