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In this paper, we propose a 3-tier ultra wide-band indoor localization system for autonomously powered sensor network applications. It consists of a large number of cost-effective tags, a number of cheap and low-power hubs and few synchronized base stations. Using the UWB characteristics and the hierarchical scheme, the localization system enables ultra-low-power, autonomous tags and precise positioning. We present how ambiguous solutions (coordinates and transmission time of an unknown node) can be eliminated with the help of the proper geometry of 4 reference nodes. A method for optimizing the number and placement of hubs is proposed. Different positioning algorithms are discussed and compared based on the position accuracy a.f.o range errors. We determine the optimal algorithm for different scenarios. Simulations are conducted to investigate the performance degradation due to timing errors.
Date of Conference: 24-26 Sept. 2007