The 3-D Positioning of Wireless Sensors in Dispersive Propagation Media

This paper describes a novel inversion algorithm for determining the 3-D position coordinates and environmental complex permittivity of wireless nodes embedded in a dispersive propagation media. In this paper, wireless sensors are considered to form part of a network for monitoring salient parameters, such as temperature and humidity, in large wheat-filled storage vessels, where the highly reflective nature of the propagation environment engenders extreme multipath effects. Under such conditions, the inherent difficulties in deriving reliable pulse propagation delay and amplitude estimates greatly diminishes the effectiveness of conventional free-space positioning methods. These limitations have lead to the development of alternative inversion techniques capable of retrieving both geometric positioning and electromagnetic propagation data. The inversion algorithm developed within is formulated as a nonlinear least squares problem in which the misfit between time domain positioning measurements and modeled data is minimized via application of a novel minimum single-level linkage optimization algorithm. In developing a more refined propagation forward solution incorporating position coordinates, host media electromagnetic properties and antenna radiation patterns, accurate positioning resolutions and macroscopic permittivity estimates are obtained under challenging propagation conditions.